MtGox incompetently managed their accounts and their method of posting transactions to the network. People discovered their failures and exploited it to rob MtGox. That is 100% MtGox's fault.
MtGox blames Bitcoin for their failures in attempt to crash the price which would allow them to recover their losses. This is the 3rd time they have triggered such a crash by the way.
The crash attempt fails because no one with sense trades with them anymore. Developers step in and point out that the failure is a result of MtGox being incompetent.
Suddenly a bot appears that exploits the defect to create duplicate transactions. These duplicates have no effect on who gets paid in transactions, or gives any advantage to hackers. It just aggravates and confuses people until one of the duplicate transactions drops off the network as intended by the protocol. The bot doing this is extremely well connected in the bitcoin network suggesting it must be operating on nodes that have been active for years.
Who benefits? Only MtGox. They have failed, are probably insolvent, and are now flinging mud at bitcoin hoping to damage the source of all their revenue. It is EXTREMELY LIKELY that they are the source of the malicious transactions spamming the network right now.
I don't blame MtGox. I blame any fool who trades with them.
I agree on that MtGox customer service is bad and that they can handle communication better. But hey, who should we trade FIAT -> BTC with now when also Bitstamp has BTC withdrawal problems? We all have to be a "fool" and sometimes trade our BTC -> Fiat at an exchange. And right now they are all crappy in my point of view. Bitstamp / BTC-E, their customer support is also not to responsive, without phone numbers etc. I am no coder, so can not tell if their implementation of teh BTC protocoll is better.