I couldn't get this research document I needed for a friend's paper, due to a spell of bad luck, I did everything I could but couldn't get it before deadline, and in no time after I didn't have his essay ready at the deadline, he left terrible, enraged messages on my phone, and now I'm laying low til he's over his thing and can't even answer calls from mutual friends or anything. It's not turned out as boring as I thought it might, though, I'm actually enjoying it kind of quite a bit.
Also, WOW, I have been surprised by his response. Has this ever happened to you? A lot of my friends are jerks, but I didn't think any were this douchey beneath it all. Very unpleasant surprise, but I guess it's better to know?
(I did finish his paper once I had the document, btw. Can't get anywhere near him to hand it over soon, though.)