In my opinion Coinbase shouldn't be held accountable. $8.3 million isn't that much in the grand scheme of things and they probably figured that with the volume Cryptsy was doing that it was possible for him to make that much.
Secondly anything that Big Vern signed with Coinbase in the way of arbitration agreements shouldn't be extended to customers who have filed the class action. They never made those agreements with Coinbase.
I had a friend get Goxed, A friend who got MintPal'ed, and a friend who got Cryptsy'd . It is terrible.