Making multiple short sale offers

[Bienes Raices]

If you're only looking to buy one house, is there an issue with making several offers on different short sales and then when one is accepted by the bank backing out on the others (after the seller(s) accept, but before the bank(s) approve). Will this alienate real estate agents or is it commonly done? There seem to be so many short sales than REOs these days I was thinking of employing this strategy.