Facebook announces Gameroom, a Steam competitor
This. If it's implemented well and they can get a lot of games on board, then it has a lot of potential. If anything steam is the unknown territory people don't want to go into, while Facebook is already a platform for connecting friends that people already use. I think it will probably fail and be forgotten about eventually because they might not understand the market well enough, but I don't think it should be underestimated either.