maximillianos - 3:01 pm on Sep 3, 2010 (gmt 0)
I've often wondered this same question. But to be honest, when I was running Adsense and Vibrant (or Kontera) in-text links it just seemed like too much advertising. It was overkill.
Sure the in-text ads didn't seem to hurt my Adsense earnings too much, but I'm sure they annoyed a lot of users, and the payouts declined to the point of me removing them. They were page bloat, slow to load and paid squat.
Removing them was a step in the right direction for our site, so I don't know if I could even use such a product if G came out with one.