i think we should worry more about the fact that mark karpeles still holds like 400-500k btc. the bitfinex hackers can't dump all their coins at once without getting noticed. they have to mix and sell their coins in batches of 5-10btc per time. with such a pace the market won't feel it.
I'd say that the market would rather feel the
lack of 120,000 bitcoins that got stolen at Bitfinex. In this way, if an exchange is hacked every month (okay, every other month), the price of remaining bitcoins would certainly hit the sky (and then the moon)...
And Bitcoin would become as rare as hens' teeth
getting coins off the market will definitely have a good impact on the price eventually, but well, these coins that are off the market right now, will at some point find their way back one way or the other. but then again, i am glad the reality is different.