I suspect there are deals, agreements, whatever you'd call them between G and Amazon to stay out of each others "back yards"..
I also suspect that if G ever did take a pointy stick to Amazon, or start treading on their toes, that they would get smacked senseless by the awoken beast..
Amazon can make deals in a heartbeat with Apple or MS or Facebook ( or whatever is the "social flavor of the moment" ) that could really hurt anyone left out of them..and Amazon are not afraid to get into hardware or software..and know a thing or two about search and really humongous server networks and datacentres..
Then again Larry can be pretty "jump in without thinking", so Google might just do some such silliness at some point..
Wonder if Larry wants to see Jeff's books etc before he lets Amazon have a trusted badge ? :), wonder what the reply would be ? ;)) if all merchants are going to be treated equally when "Google trust badges" are being dispensed that is ..:)