Haven't had it happen to me. They usually ask "hey is that an ipad?"
But i appearantly have an iphone/ipod aswell. Could have sworn it said Google on the back of the phone
People connect a brand to a device, and once that's done it takes ages (if ever) to get rid of.
Kindle and ipod are just the latest example's. Think of ducktape, hansaplast etc etc aswell.