On eBay, sellers have an incentive to spell their item titles correctly so that they show up in searches, and buyers have an incentive to search for typos (as has been said before, you can usually pick up a bargain "pLAm pilot" on eBay). What would happen if eBay started incorporating typo search into their interface? The incentive for proper spelling goes down and the typo discount goes away too. The secondary effects are more careless spelling in auction descriptions and the end of services like Auction Bloopers.
Mokalus of Borg
PS - I'm thinking of looking for a bargain "iopd touch".
PPS - But all the auctions I found were spelled correctly.