Under what circumstances is it permissible for a man to wear no head-covering?
If one is in a place that is experiencing anti-semitism, for example, does one need to wear a hat if one feels endangered wearing a Kippah? What if it is culturally offensive to wear a hat - say, indoors, or meeting an important person?
Does it make a difference if one is seated? On that note, may one eat (or for that matter make a Berachah) without a head-covering in such a case?
(If this is too broad, I can break it up into smaller questions, but I think the questions are interrelated enough to keep together.)