EA's Origin digital storefront has a long way to win over the gaming community. One feature that may help is the discovery that certain Steam keys for EA games can be used on both digital platforms. PC Gamer reports that Steam keys for Battlefield: Bad Company 2, Dragon Age: Origins, and Mass Effect 2, among others, worked to activate Origin games as well. Some games (like the original Mass Effect) didn't work in testing, though, so the keys aren't always universal. They seem to work more reliably with recent titles.
The report also notes that Origin launches the Steam version of Dragon Age 2, and the Origin client auto-detects installed EA games. Since it can already do both, it's theoretically possible for the service to read EA games in your Steam library and populate your Origin library with them.
EA's push to give Origin platform-exclusives has been met with mixed reaction from fans. Star Wars: The Old Republic will be an Origin-exclusive digital download, and recent reports indicate that Battlefield 3 won't be coming to Steam -- though EA is reportedly going to make it available on other digital platforms besides their own.