Well keep in mind that hf19 hit the steemit platform. Also with the increased price of bitcoin there has been a massive increase in the use of cryptocurrency in general. If Poloniex didn't have the infrastructure to deal with this new increase then they are struggling to keep up. I am holding out for Poloniex as their rates have been so reasonable, but In the meantime I am looking for another exchange to handle my steem. I mean, rent does have to be paid after all ;)