Standing up for your rights can be a pain. It certainly takes fortitude.
Thus, the events set out in TigerDirect Unlawfully Restrains And Verbally Abuses Customer For Not Submitting To Receipt-Showing Demands.
One little warning: whether a shop can demand you show a receipt to exit is most likely a question of state law — and yours might be different from his.
I once satisfied myself that Florida law does not allow a normal merchant to prevent me from exiting a shop with goods I've paid for, even if I choose not to show a receipt, so I don't show receipts when asked to at TigerDirect or CompUSA. (As I'm not admitted to practice in Florida, you shouldn't consider that legal advice.) And I'd note that I'm not sufficiently clear what the Florida law is for stores that don't admit the general public — so I do show a receipt at Costco, which requires membership before you can shop there.
Why, one might ask, would anyone be a pain about stuff like this? Are we not sympathetic with merchants being stung by shoplifters, thieves whose actions just force higher prices on the rest of us? I am sympathetic: they have a very legitimate beef, but have chosen a bad way to deal with it.
As our good friends at the Canard Enchainé say about press freedom, La liberté de la presse ne s'use que quand on ne s'en sert pas (“Freedom of the press gets used up only when unused”), so too with other freedoms.