How does the buyer protection work?

For instance, there's an iPad 2 up for sale right now with a min-bid of 5btc. At the current exchange rate, that's a really cheap iPad 2. If the auction closes and the exchange rate doesn't fluctuate enough for that person to make as much of a profit as they were probably hoping, what's their incentive to follow through?

Is it simply an escrow mechanism so they won't receive my btc until I approve it, or something else?

(I'm very tempted to start bidding on the serious items, but I don't want to get scammed and this sort of thing is prone to that.)