Amazon has a patent to keep people from comparison shopping in stores
It shouldn't matter that this is an obvious thing to do or easily circumvented (for the time being).It is 1) an invasion of privacy and 2) anti-competitive behavior.Version 1 may be easily circumvented, but future versions could easily be tighter and more difficult to circumvent.  For example, a contract with the mobile providers could make this something that no longer depends on in store WiFi usage.This is the sort of thing that should be stopped in its infancy.