A few days ago Dragon Age 2 mysteriously disappeared from the Steam store, right around when the Legacy DLC released. If you've been keeping up with EA lately, you would assume the most obvious reason for that is their own digital distribution service, Origin.
History is repeating itself, because this same thing happened with Crysis 2 just after the launch of Origin in June. Back then, EA claimed that they had nothing to do with the decision and that it was all on Steam, saying that "Crytek has an agreement with another download service which violates the new rules from Steam and resulted in its expulsion of Crysis II from Steam"... before plugging the game on their own digital store.
It's a similar story today with DA 2. EA senior VP of global online David DeMartini stated, "unfortunately, Steam has adopted a set of restrictive terms of service which limit how developers interact with customers to sell downloadable content." He hopes "to work out an agreement to keep our games on Steam", but at this point I really find it difficult to believe that this has anything to do with Steam's ToS. If the culprit walks like Origin and talks like Origin, then it's probably Origin.