It's funny... the NFS series had become so rubbish, that I had stopped paying any attention to those games. With SHIFT, they've gone to quite a lot of effort to gain the interest of people like me, and they've done so well that I had this down as a probable purchase. But now... no sale, no way.
In-games adverts are never okay. Any time a person says "ads are okay so long as they're done right" is absolutely fooling themselves. You are explicitly talking about giving marketers control over game content! SBlat points out an absolutely ideal demonstration of what that means even in a game where people are expecting to see billboards and such forth.
The "perfect world" version of in-game advertising that some people have in their heads is not the reality. The goals of marketers and the goals of game designers are not the same, and you CANNOT put them together without damaging the game.