I just found this: http://www.gamesindustry.biz/content_page.php?aid=23148

Just to shorten it:
Sony's president of worldwide studios Phil Harrison has confirmed that the PlayStation 3 will support over 1000 PS2 titles when it's launched on March 23.
With the PS2's emotion engine - the CPU - taken out of the PlayStation 3, Sony is relying on in-built emulation to play PlayStation 2 games on the console, and it's confident regular updates will mean a steady stream of classic titles for the machine.
"We're working to introduce a resource to the Web to detail which titles will have backwards compatibility. And as we make firmware upgrades, we will be able to add to that list," said Harrison
So there pulling an Xbox360 with the bc. And the list can be updated with updatse, so there will be BC, just limited.