I often wonder that adsense have captured the market just because it is by google. i have noticed that there aer other ppc programs and they are not that bad. Infact adbrite is quite good.I think people should start thinking about it.
Unfortunately, but Adsense doesn't have any equal competitors at the moment. But we all hope someone can stant with them...
Adsense is MUCH better although they can be rather fussy over things, and if you don't follow the rules, you WILL pay the price. (Quite literally) Only use adbrite if you get banned from adsense, as suggested before.