Pretty happy I found Steemit recently, as it has opened my eyes to Poloniex. This is feeling more and more like Mt. Gox with each passing day. Maybe that isn't quite fair, as Mt. Gox truly was incompetent. Poloniex may be a case of biting off way more than they can chew. One possible vector not mentioned is that Poloniex is likely still filled with bugs across their expansive platform. Managing that many currencies, that many wallets is likely to be a monumental task. The slow response from support reported across many channels is not encouraging either. My personal issue is quite relevant and highlights one bug:

Recently I closed multiple margin positions. I shorted ETH, LTC, XRP, and DASH vs. BTC. After closing all of my positions, a few hours later Poloniex still thinks I have some position and is still calculating a borrowing cost after I have withdrawn all funds possible:

Total Margin Value 0.01475918 BTC
Unrealized P/L 0.00000000 BTC
Unrealized Lending Fees -0.00000004 BTC
Net Value 0.01475914 BTC
Total Borrowed Value 0.02176298 BTC

Mind you I have no positions open. The amount of "Total Borrowed Value" is the amount Poloniex believes I still hold a position for, yet I have no open positions, short or long. At this stage I am uncomfortable having any funds on Poloniex and likely won't be going through the grueling support process for the small sum currently stuck in margin-limbo.