Common enough to have a name of it's own: the `Second Chance' scam. Ebay really does have a policy whereby the item may be offered to the next highest-bidder if the transaction with the high bidder fails, but a scam has developed to try and take advantage of this. See
http://www.pacglass.com/second_chance_scam_-_aba.htm
for more info, or google "ebay second chance scam".
Chris