It's a lot of fun when the price rises and in the exact second you're supposed to receive the bitcoins your transaction gets cancelled.  It's just like going back on your deal.  If I make a deal with someone, for example I promise to give them some cake next friday and take some money in return.  I take the money, and when friday rolls around I give him back his money because I think he's a high risk customer, although the price of cake has risen in the meantime.  The guy I made my deal with has a house full of guests that will not get cake that day.  I also offer a help-line for him to call but there's no one to answer until some unspecified time in the future.

If Coinbase were honest, they wouldn't cancel transactions in the last moment and refund the money.  The last ebayer that did this because I order from him from a "high-risk" country got a NEGATIVE feedback from me.  If a transaction is high-risk DON'T ACCEPT IT TO BEGIN WITH!  That would at least be honest!