Nice top level summary of a really big and interesting space.

So big and interesting that Google, the company with the largest market cap, is the dog. Regardless I think Jim Crowley, the CEO of BuyWithMe, pretty much got it right when he told Crain's "There is room for six of seven large players as well as niche players."  

But Google the underdog? How do you suppose they are going to change that? If I were Jim Crowley I know what my answer would be.