Isn't there tremendous opportunity in pre-foreclosures right now? Knowledgable feedback appreciated

[Tommy R]

I don't get it- there's over 4 million properties that are over 90 days late or in pre-forclosure (source: doctorhousingbubble.com)

Wouldn't banks _love_ to get these properties moved? (or not? And why?) I understand they can't release too many properties on the market at once as that would saturate the market, cause home prices to drop and cause other homes to strategically stop making payments...

But still, what is our major obstacle in acquiring these properties for cheaper than at foreclosure auctions?
(is it that we have to convince the current occupants to leave? What if it is abandoned?)