seems like they'd want to drive the value up, not create a fear that would result in bitcoins losing value

I'd probably say that their attack (if it was in fact them) was a good thing for BitCoin in the long run. It's not really helpful to have the value rise if people don't take security seriously, and if the economy becomes heavily centralized. If in the future there are lots of small exchanges, with good security, the value of BTC's will go up, but this is in a time frame of years, not weeks
