First off, the guy was never arrested. Just because you are led away in handcuffs does not mean you are under arrest. The cops have a right to detain you if they suspect you are involved in a crime. The cops had reason to believe so because the Best Buy manager told them he truthfully believed the guy was attempting to commit fraud.
Second, to klee58 (and maybe others), if I remember this "scam" correctly, the people go into Best Buy with the following:
1) A receipt from Best Buy online showing they put in the order for the card
2) A copy of a receipt that someone else posted to the internet indicating they successfully made a price match at another Best Buy store.
It's #2 that got this guy into trouble, because it was most likely a printout of an image from the internet, not an actual receipt printed on Best Buy stationary. He could have easily doctored the image before printing it out, and that is the grounds for the belief of fraud. Also, don't forget that we are only seeing one side of the story, and the guy posting is certainly not going to post anything that could incriminate himself, regardless of what actually transpired.
Was the Best Buy manager acting in a heavy handed manner? Yes. Was he wrong? According to the law, no. Am I tired of hearing about this stupid video card crap? Most certainly.