I suspect it's already happening...I once wrote a script for a girlfriend who wrote an online journal that sent visitors to various pages depending on their IP address (well, the first two parts anyway - testing for ISP). This allowed her to send her parents and other relatives off to a page telling them to screw off! :)

The thing is...who knows? It's hard to tell how many people are doing this sort of thing. I suspect that I wouldn't mind terribly much if I went to (for example) eBay and all the prices were in Canadian dollars (since I'm in Vancouver). I might get a little annoyed if I went to Google and my searches came up only with Canadian sites though. It would remove the effectiveness of the service, rather than enhancing it.

Kickstart