I haven't been doing much on most of the exchanges lately. With the alt-coin apocalypse, so many of the coins that have been traded quickly became more or less "worthless", so I consolidated all of my holdings primarily into BTC and called it a day. I'm also basically done with GPU mining, as the best returns only just pay for power and may a bit extra.
Anyway, I just saw today that MintPal, one of the more well-known cryptocurrency exchanges (and by no means one of the best, as they've had hacks/problems in the past) is apparently going away. Well, maybe not quite, but the managing company is filing for bankruptcy and they've "sourced a new management team" for the site. There have apparently been some additional problems with missing/lost balances over at MintPal, and if that's the true I can see how that could quickly lead to closing shop at this stage.
On that note, with so many alt-coins basically dying and becoming worthless, I suspect we'll see something similar happen with many of the exchanges that primarily deal in alt-coins. Again, I've pulled my coins off of all of the exchanges (well, except for coins that are basically worthless -- the exchanges can keep those if they'd like), and I'd strongly suggest others do likewise.
For that matter, if you're in Bitcoin for the long haul, you might want to just move your coins into cold storage rather than trusting Coinbase or any of the other big names with your holdings. I haven't gone that far yet, mostly because I still do things with my Bitcoins (like buying Hashlets, ASICs and other goods), but better safe than sorry. And if a company you're doing business with seems to be acting a bit crazy, perhaps it's because they are?