[ilovecars]

Yeah, I agree, it's not a monopoly. But they do have the most advertisers, so the alternatives aren't as good (for now, at least).

[ig1]

Both AOL Advertising and Tribal Fusion have huge display ad businesses (both reaching >500million people) with vast number of advertisers.

Many large content company only use Google for remanent advertising as the Google CPM is often pretty poor compared to other options.