I was once escorted out of a grocery store becasue I was standing in an aisle comparing prices using a calculator. The assistant manager approached me and asked me what I was doing, when I explained that I was comparing price per unit on olive oil he told me I was not allowed to use a calculator or record prices from the store in my price book which I had out.  I told him that was ridiculous policy and he escorted me out.  I have never returned to that store, and I did write a letter of complaint to the manager.  I even included in the letter how much money they would lose each month because I would no longer shop there.  I never got an apology or any kind of acknowlegement that they were in the wrong.  Ever since then I have been wary of big chain corporate grocery stores.  They obvioulsy have something to hide and don't like it when the customers manage to save a buck.  If anybody would like to know what chain that store was, ask me, I'd be happy to divulge in private. 

That's absolutely absurd!  I've never had a problem like that... and if I did, I'd be going to the nearest news station with an investigative reporter if I got no reaction from the company.

I bet they thought you were engaging in corporate espionage - they thought you worked for another grocery store instead of being a regular customer. Guess the joke's on them.