I use the Incognito Window daily to get a clean slate for many purposes, like getting unpersonalized Google search results (Wigflip stuff comes up higher for me than for everyone else) and using alternate logins on sites where I have 'em.
I hate, hate, hate going to Shaws, but sometimes it's the only option. The prices are awful unless you have a Shaws card, and I'm never getting one.
The past half-dozen times I've gone there, though, and said "No, I don't have a card, no, I don't want one," the clerk has scanned their own card or a card from the top of a stack of new, to-be-issued cards! Doesn't that screw up Shaws customer profiling schemes? I wonder if clerks ever get in trouble for doing that.