While not all EA titles have been pulled from Steam, there are two games that are rather obviously missing from the EA lineup: Crysis 2 and Alice: Madness Returns. EA has already promised that future titles, such as Star Wars: The Old Republic will be exclusive to Origin, though it would appear that their plan includes games that were previously released on Steam, though some smaller digital distributors still have access to games pulled from Steam.
The move by EA to keep certain games exclusive makes sense on a business level. By only offering certain games through their site, they will be able to attract more consumers and using Star Wars: The Old Republic will attract quite a few. Unfortunately for the company, EA is not a fan favorite, as a recent boycott demonstrates, and while EA has addressed the issue it remains to be seen if that will be enough to get those, and other, fans on board.
Update: In a statement sent to IGN, EA explains that Crysis 2 being pulled from Steam was not their decision but rather a conflict of interest between Crytek, Steam and another, unspecified, download service.