You walk into a random corner store for Tylenol and see the bottom of a cut-off box of cereal with pills inside. A cardboard sign in front of it says "Tylenol" and there's a logo clearly printed off a website gluesticked to the box. The pills are plausibly the right shape and color.

You buy a few and take your Tylenol without a second thought—right?

Maybe not. If that seems ill-advised, please don't propose the same for websites.