In the latest twinkling that Sony PlayStation 2 backward compatibility is never truly off the table for the PlayStation 3, Siliconera has word that Sony has filed a patent that outlines an external peripheral of some sort that when connected to the PS3 allows it to play PS2 games.  Think of it as a "PS2 Player" to borrow some terminology from Nintendo's Game Boy Player add-on for the GameCube.  Here's a bit of the story:

Most PlayStation 3s are not backwards compatible, but Sony may be investigating an external adapter to act as a bridge. Japanese message boards are buzzing about a patent filed by Sony Computer Entertainment Japan for a new generation to previous generation console adapter. We checked the Japanese Patent database to verify and a patent indeed exists.  A schematic of the proposed adapter (200) shows the device has its own processor, a DVD decoder/emulator, sound processor, and graphic processor.

It seems to me that if I wanted another box hanging around in my home entertainment cabinet, I'd just stick with my PS2.  I don't know about you, but to me the appeal of PS2 backward compatibility is that it helps to unify my gaming library and removes the need to tie up valuable space with another box and more cables.  At this point, I say either build the PS2 capabilities directly into the PS3 case or let's just move on.