@pine - very interesting topic.

What are you ashamed of? Who taught you to be ashamed of that particular thing?
What are you shameless about, that others aren’t?
Do you think people should be ashamed? If so, who and why?

I am ashamed of :
- not being well informed, not mastering a certain topic or not finding the right words to express what I do know - it might be a form of exposure, I think;
- showing affection to people who don't feel the same - so, pretty much what you mentioned above about unrequited love and rejection ;
- acting in an inappropriate way, especially in front of people I care about - again probably a form of unwanted exposure of certain flaws;
- failing to do a natural, easy thing that anyone should be able to do. Like dancing. Or peeling potatoes the way they should be peeled. 🙂 I have very low dexterity. Way below average. And I feel ashamed when others can see how freaking low it actually is. 🙂
Maybe there are other situations in which I feel shame, but these seem to be the most prominent ones.
I suppose my parents and close relatives, as well as teachers and - to a certain degree - the media taught be to be ashamed of these things.
I don't really feel ashamed of being naked. I mean...I know many girls who have different worries about their bodies, which I don't. My body is not perfect either but it's not something that concerns me that much.
I am also not ashamed of not wearing make up, not being dressed fancy enough at certain events, being late, not knowing something that I am not supposed to know (for example I feel ashamed if I don't know what law applies to a situation but I don't feel ashamed if I don't know who the Minister of Education is - because this does not impact my work or hobbies and can also not be considered general culture  - so I don't need to know it ).
Failure usually makes me feel rather frustrated than ashamed and I also am usually able to avoid it by winging it. 😛 :))
Regarding guilt - I feel it only after doing something clearly wrong. So, it's different from shame. Guilt seems to be easier triggered by wrong deeds and shame by our weaknesses becoming visible to others. Guilt is less dependent on what other people might think - it can come to the surface when we can see we did something that is not aligned to our values, even if no one else knows.
Shame on the other hand seems to be image related. What will this person think of me after she finds out I did that? We have this saying in Romanian - the earth swallowed him because of shame. Not sure if it exists in English too? It's exactly like this, you want to disappear completely. While guilt would rather make you want to atone.
Should people feel shame? I think so, they should. Shame is like fear...it can protect us from social situations that could be damaging for us.
There should be a balance and a certain correlation between our feelings of shame and the social rules that we live by... so, it is healthy to feel ashamed of getting drunk and starting to make stupid jokes about people and to instigate others to attack them 🙂 but it is unhealthy to feel ashamed because your cat is meowing loudly in the taxi, as long as the taxi driver knew he will pick up a woman with a cat. 🙂
I mean, shame should ideally just help us act in socially appropriate ways (enough to not be kicked out of places :)) ) but not make us constantly feel bad about minor things that are not really under our control. Also, shame should not make us trample our values in order to align to what others expect of us.

Mm, I would like to say a few things here.
Having been the target of Self-directed shame for many years now (over something I truly had no control over), I know how deeply unhelpful and damaging shame is when it is wrongly directed. However, I'm not ready to write off shame as a useful mechanic for society, and in fact I believe it can play a vital role in societal well-being (and in a legal system increasingly dominated by wealth it must necessarily be so). The example that comes most easily to mind for me is the #MeToo movement, in which I understand part of the movement represents a collective psychic anger at the failure of legal systems to actually provide justice for the survivor and for society. It must always be remembered that when the legal system exculpates a legitimate predator of wrong-doing, it doesn't just harm the survivor (which is bad enough imo), it harms all of society by releasing that predator back into the wild to introduce more evil into society.
The example of which I could speak more at length actually concerns the police department in Dallas, Texas. I've mentioned this before, but I worked in one of the most heavily trafficked psych ERs in Dallas, and so I dealt with the DPD (Dallas Police Department) and the aftermath of their actions on a nightly basis. Their smallest and most frequent betrayals of citizens' trust involved telling individuals they detained and brought to our doorstep this lie, "Oh, you'll just be there for a quick check-up from the doctor, nobody stays there for more than a night." I know this because the patients would tell these stories to me, often becoming extremely upset once they learned they were in for a minimum 72 hours, and I would be the one to have to calm them down now that the liars had left. And these stories were so widespread and so consistent I knew them to be true. In fact, these same officers that lie to the citizen all the way to the hospital had to physically sign the documents committing that person to the hospital for at least 72 hours once they arrived! They simply couldn't be bothered to deal with the repercussions of telling the truth, and so lying was their Standard Operating Procedure. (I also witnessed much, much worse behavior, one incident being egregious beyond measure on the officer's part, but no one was directly harmed in that incident and I don't want to be dragged into court myself, so I will pass those over for now.)
This example came to mind because DPD was recently in the news for inadvertently murdering another mentally ill citizen (a schizophrenic who called 9-1-1 for help because he was off his medications and deeply scared). After watching the three minute video released (which took three years to be released in the first place because DPD tried everything they could to block it legally), I can safely say that the officers did not intend to kill that man, they just simply didn't care enough for his well-being not to (repeatedly jamming their knees and body weights into his back to keep him from moving, and never bothering to check pulse or respirations as I'm certain they are trained to do). There is a cop culture in Dallas (and likely in many other places) that any possible reduction of harm to themselves is worth any harm to a citizen.
Now, in America the legal system has enshrined law enforcement to such an extent that there is no justice to be found within its walls almost as soon as the police officer(s) become the focus of a case (just Google some of these cases; no matter the severity of evidence, the officer is almost always acquitted by the court because of how the statutes are written in the first place to preclude as much as possible the possibility of an officer being found guilty in a court of law. And if the Back the Blue Act is ever passed, I believe America would then be most properly understood as an official police state).
Every officer involved in the killing of the schizophrenic citizen I mentioned above is already back to active duty after a one month suspension. So, lacking legal recourse what is left for society to do to correct such horrific offenses as wanton murder without consequences? Shame. Police officers and police departments are still filled with individual human beings, and individual human beings can and should be shamed if standard recourses have failed. If I had a sufficiently elevated platform from which to shout them down and shame their behavior, I would be happy to do such a thing myself, and indeed would be proud of myself for having done so.
But, one last very important distinction with shame: I believe shame should be directed at behaviors rather than individuals, so that the individual can correct the behavior without feeling ashamed of their entire person. So, I would never want to say "All cops are shit! Death to cops, we don't need police!" No, I think that's idiotic in the extreme. What needs to be said is, "You're here to protect us and you're failing. Here is how you're failing, and if you continue to refuse to acknowledge or correct these failures, we will continue to bring shame upon you; peace of mind we will attempt to deny you as long as you deny it to your citizens."
Edit: Oh, yes! And here is a recent real-life example that I would consider to be an act of shaming that is done with the express purpose of improving the world and achieving justice when the formal, institutional routes failed:

Edit 2: And it worked; by galvanizing Congress and bringing the issue into the national spotlight, public shaming succeeded where "following the rules" had mostly resulted in more sick and dead and more excuses from Congress as to why so little was being done. I just checked the status of the bill and on 07/29/19 the bill became Public Law, creating a permanent Victim's Compensation Fund for the 9/11 First Responders.