Microsoft sold Massive, true, but they have their own in-house in-game advertising team. "In and Around Game," actually.
Ads in games can work fine. They just rarely do. I typically point to Def Jam as a game that got this right, as they were subtle and fit the world. Of course, that game is now 8 or so years old and was, in itself, pretty much just an advertisement, so it being the best example I can come up with says quite a bit.