Consumer Advice

There's a lot a website can tell about you just by where else you've been surfing. I've noticed this for quite some time as well. For instance last week I was buying some bike parts online from ebay, and for the rest of the night i kept getting biking-related ads wherever I surfed. Then I'd clear my cache and history and I'd be getting ads about something completely different, like say business schools (all of which are within 100 miles of me).

Can't figure out why they'd quote higher prices just because a user has a Mac. I do know that in my experience right-wingers tend to use PC's and PC's are used widely in the corporate world. Is this possibly the beginning of political discrimination?