Amazon recently filed a patent for a system wherein while someone is shopping inside of a store, and using that store's wifi connection, the store owner is able to inspect the wifi packets to see if a competitive product is being viewed and then issue a "control" action in response.

Basically if you want to price shop while inside of a retailer, they'll be able to block the action from happening.

http://patft.uspto.gov/netacgi/nph-Parser?Sect1=PTO1&Sect2=HITOFF&d=PALL&p=1&u=%2Fnetahtml%2FPTO%2Fsrchnum.htm&r=1&f=G&l=50&s1=9665881.PN.&OS=PN/9665881&RS=PN/9665881