UK contract law ...
IIRC when the Koday camera fiasco happened (which never made it to court IIARC) various lawyers pointed out that a "contract" to between two parties can be voided in the case of error or omission when the error or omission would have been obvious to either party.
Put simply, just because retailer X offers a 42" HDTV for 1p on their website, and take an order and confirm it, doesn't *automatically* mean the purchaser would win a contract dispute in a court of law. If the judge finds that the mistake was so obvious as to be apparent to the purchaser, then he can declare the contract void, and retailer X does not have to supply the goods.
In an item worth 600 GBP was accidentally priced at 450 GBP, then the retailer would be on shakier ground, as it's less obviously a mistake.
Unfortunately for the (UK) something-for-nothing brigade, them more stories like this are reported, the less likely it is a judge would accept that a purchaser had a genuine belief that a ridiculous price was not a mistake. In fact, (memory vague here) I believe that was one of the factors which led Kodak to eventually honour the camera orders, as it was pointed out that online shopping was a relatively new experience, and a lot of punters could have genuinely believed the offer was a promotional deal.
Incidentally, this tweak of UK law also puts the kybosh on those people who use such mistakes to order 100 high-value items at 1p ... I can't see any judge in the land accepting that you believed the mistake was a genuine price if you then order 100 !
You can tell it's Friday, and that damn report is *still* running !