netmeg - 7:38 pm on Feb 9, 2013 (gmt 0)
Think of it from an advertisers viewpoint - why bother with the lesser ad networks when you can work with Google? Unless for a variety of reasons (ad content, site content, been kicked out, can't figure it out) you can't.
Your best bet is if Facebook ever decides to do an AdSense kind of thing. They'll have to get over the privacy hurdles, but THAT would be a barn burner, because they have a lot of targeting that Google doesn't.
Dunno if it will ever happen, but that's the best bet for a viable competitor in my book. Bing just can't seem to make it work. (And it's not like they don't have the resources)