Because Coinbase is so huge, you can expect big issues on their stability during pumps and dumps, when most traders go crazy.
There is a lot of good exchanges to replace Coinbase: Kraken, BitStamp, GDAX, Cex.io, Gemini, Bitquick and more, most of them have great mobile apps.
I wouldn't recommend Poloniex if he only want to trade USD-BTC, same goes for Bittrex and Shapeshift.
That's a poor excuse.
Even the big banks do this shit when the currency prices are too volatile. I can understand why the banks are doing this (to not take the loss) but a bitcoin exchange is not a bank. It is more like a forex trading platform.
Btc-e is having shitty issues lately but from what i see you won't have a problem like the one you had with coinbase at least.
