I've lost count of how many threads I've read which start out with the OP asking if they or their friend is BU. Then over the course of the thread more and more negative information is written about the "friend" until you're left with the impression that the OP would find hanging out with Pol Pot, Hitler, Katie Hopkins and Donald Trump a pleasant change.
If threads in here are to believed there seems to be a worrying number of MNers who think that friendship involves being let down, lied to, taken advantage of, insulted, stolen from, gossiped about or generally treated poorly as a matter of course, without ever stopping to think "hang on, why am I still considering this person a friend?"
(An interesting - and, I'm sure, completely coincidental
- phenomenon I've observed is that often the friend's true colours aren't revealed until after a majority of posters have suggested that the OP is the one BU.)