It’s very obvious that Mass Effect 3 on PC will be launching on Origin, which is EA’s answer to the Steam service. EA has also said that all copies on PC will require Origin activation. Meaning, if you don’t have origin on your PC already (which is nearly impossible with any new EA Game that has launched since), get ready to download that client to activate your copies of Mass Effect 3. This info comes from a post made by Chris Priestly on the BioWare forums which also points out that Mass Effect 3 will NOT launch on Steam…atleast for the time being. Here’s a direct quote from the post:
4) Will ME3 be available on Steam?
During initial release Mass Effect 3 will be available on Origin and a number of other 3rd party digital retailers, but not on Steam at this time. Steam has adopted a set of restrictive terms of service which limit how developers interact with customers to deliver patches and other downloadable content. We are intent on providing Mass Effect to players with the best possible experience no matter where they buy or play their game, and are happy to partner with any download service that does not restrict our ability to connect directly with our consumers.
This sucks for people who might have had plans to buy the 3rd game through Steam, if EA and Valve can work something out, it might not be out of the question.