Where the complaints should really go is the NFA (National Futures Association) and the CFTC (Commodity Futures Trading Commission) as Coinbase is clearing running a book or market maker without the proper licensing. While they may be in a loophole due to the US not recognizing bitcoin as a currency, they do price it as a security against the USD which should fall under the loose definition of a CFD or contract for difference.

And as market makers go, they are sloppy to say the least.

Cheers...