We're seeing similar activity in an area that we're still stuck with a house and renting out (don't buy houses in mid-07 kids, that market hadn't crashed yet).

We've been approached by a few with very low offers (via an agent). I've been tracking sales in the neighborhood and every month or so another 4-5 houses that were never on the market are sold. They are then rentals shortly thereafter. I've been pretty surprised at what things are still renting at, I thought it would plummet prices (and it still may) but they seem stable at about .6-.70 cents/sqft. It's not the Bay Area or even the nicest place in town but I find it peculiar that large investors would be interested enough to buy up 1% of the houses in an area every month or so, though the prices seem pretty good and that'd be a great rate of return.