Personally I've never had cosplay drama myself, although I've witnessed some pretty ugly scenes going on with other people throughout my cosplay 'career'.
Last year I watched a girl in a Sora cosplay break down in tears because I guess someone had bought the last item in the vendor area that she wanted. Out of curiosity I'd asked her friend if she was okay and she'd explained that she had asked the vendor to save a prop for her, but toward the end of the con when the vendor thought she wasn't going to have the money he ended up giving it to someone that was willing to buy the item up front for more than the item was initially worth if they could purchase it. It sucks, but I understand that if the girl didn't pay for the item after the three days they were there that's why the vendor would have just decided to sell it.
Other than that the only recent cosplay drama I've witnessed was that on a thread I frequent on BBnet a male cosplayer had asked for advice on his interpretive Ciel cosplay. Then after people attempted to offer critiques he got angry and has been victimizing himself ever since.