In my opinion: -They will control the price of the market of similar product - Monopoly is bad for consumer What yours ? Can we stop them?
They are not a monopoly, so if they start paying/charging/providing badly a competitor will overcome them.
They are not a monopoly, I think they treat the small time publishers like ****, the big time publishers get first rate service from them.
Good thing is that google does things logically, so if you work hard you can be on top of their SERPs unlike live and to a certain extent yahoo which seems to make random decisions on how to rank sites. And since google dominates you don't have to worry about losing much traffic if you don't rank well in yahoo and msn.
Best : they will have all the resources to come up with the best search results Worst : we will have to follow any guidelines they made... even if it sounds stupid!