Sounds like another Cryptsy going on at the time.
doesn't look like it though!
the problem with these exchanges is that they only provide servers powerfuil enough for a certain number of users which they usually get.
when there is a fast rise or fast fall like this the traffic grows and obviously they can't handle things anymore.
there is also DDoS attacks.
and on top of that it is possible they have ran out of funds again because people also buy and withdraw at times like this at the bottom and the exchanges go dry. it is easier to say we are down than to say we cant cover withdrawals.
. I think this attack is also one of the cause the price is going down. People are in panic and want to get out. I do not think coinbase can be affected this much by that attack and maybe you are right in your other point, they run dry and preventing withdrawals.