my secretary and I noticed this last year when we were both searching for long haul flights. and we do the same thing, clear the cookies. but data point. We were in chongqing china Wednesday, and I checked email using a throwaway china unicom data sim as a mifi and vpn to lax on a mac in a private browser session. Thursday i got a targeted tripadvisor email about hotel deals in Chongqing while I was on my way back to ORD. I think lots of these companies including AA know a ton about what we buy and how much we spend. You just have to escalate your online shopping techniques to see if you are getting the best deal you can.