The retail seller doesn't wait for confirmations after you swipe your credit card. That takes 3 days!
The retailer gets a confirmed authorization immediately.
That doesn't guarentee they'll get the money though, that guarentees you're approved and under your credit limit. You can dispute the transaction, and for relatively small amounts the credit company will just give it to you, and the store can't really do anything because taking you to court would be too expensive. Do it too frequently, though, and your credit card company will start bringing you up on fraud charges.
