[quote name='omyard']I can only guess its to track returns. I know when I worked at Wal-Mart you needed to present valid ID for a return because you were only allowed so many in a period of time without a receipt. Even if you had a receipt you needed to present ID because the system was setup that way. So I'd assume Best Buy is the same. It doesn't matter that you paid with credit, used a reward zone, etc... It's setup 1 way so that the cashiers don't have to learn how to process reruns different ways.
I can't say for sure, but that's just a guess that makes sense.[/QUOTE]
As a former Best Buy employee, it's to prevent against people who are dumpster diving for receipts and grabbing the thing off the shelf and returning it like they bought it. It can be overridden however if the return is for, say, redeeming a video game pre-order or if the person returning the item happens to be underage.