Beware of Poloniex,
They use bots to pump and dump coins and ponzi schemes, at the moment the exchange is pumping DASH which is a ponzi scheme, they create these big pumps, attract investors who short them, them keep them stuck for weeks. If you dont know Poloniex is designed to suck in investors, use bots to create fake volume.
i disagree with DASH being a ponzi scheme, there are lots of things wrong with that coin but being a ponzi scheme is not one of them. and yes DASH is not pumped big time and it will dump.
also poloniex is known to be the place for pump and dumps and they do it themselves too. everyone wants a piece of the action afterall! and when they do they use bots,...
but i disagree with what you said about "stucking traders"
they may finally pull a MtGox on us and run away though.
I think holding money on a website is a stupid idea. Especially if it's a trading website that's exposed to hacks, or you can be the one exposed to a scam.
It can be even the best known trading website and it's still not a good idea. The best place to hold your money is in your pocket. When you want to trade it, deposit, trade and withdraw at the end of the session. There have always been known hacks and thefts and criminals aren't always found. Bitfinex is a good example - you don't even know if it was the team that took the money away or a real hack. If it happens, it happens because people are holding their money there as if it was their wallet, not someone's website.