Richards spends the rest of the post explaining that in-game ads work, are easy to implement and, the kicker, gamers actually like them. He notes that all ads are placed with an eye toward realism, saying that "gamer satisfaction" is paramount and that all ads go through testing before being added to a game. Furthermore, he suggests that ads actually enhance the experience, contributing to realistic immersion.
Regardless of your feelings toward game ads, one thing is clear: They aren't going anywhere. Massive has already announced a fairly, well, massive lineup for this fall. Let's just hope Massive keeps the ads unobtrusive, unlike some other in-game ad companies.