I too was ripped off by coinbase. Bought 10BTC last Friday at $424 each (instant buy). Was sitting on them til while the price was soaring. Come Wednesday, they cancel my transaction. I would have sold while it was hovering at $850. $4,000 profit gone. Just like that. I contacted support multiple times with no response. Also tried from a different email address and they didn't respond. Now any time I try to purchase they cancel the order. Stating it is a high risk transaction. I have made eight purchases from them since January. Now the last 2 canceled and its like I'm on some blacklist.