Look like some obvious market manipulation. I don't think it's a hacker network. They've nothing to gain for destabilizing prices. They could easily use their botnet to mine coins, steal passwords etc.
And I wonder why I still can't post in other forums.
There is no reason to expect this isn't a "hacker network". Buy tons of coins, wait for price to be drive up and then sell tons of coins and DDOS the site. People panic on other exchanges and start dumping coins, people get back on mtgox and all put sell orders in because they think they're losing everything and the market continues to spiral down. Price hits a bottom, "hackers" buy it at a discount. They just profited.
I am done with Mtgox after today. For whatever reason they are a target, I assume because they claim to do 80% of all Bitcoin trades. If I had my coins with another market I would actually be able to act and try to get in on some of this action.