professorhat:
I'm not a contract lawyer, but the differences are clear between purchasing in a shop and over the internet. In a shop, a human being takes your cash and then gives you the goods - that's where the contract is made. With a website, there's no human being to detect the error until it comes to shipping time - that's when the mistake is spotted. Since the goods haven't been handed over (or dispatched), there's no contract at that point so they can lawfully refund you your money and not ship the goods.
Believe me - these Ts & Cs for internet companies have been around a fair few years and if the above wasn't the case, it would have been changed by now.
The professor is right. I've studied Contract law and in a shop situation, the "acceptance", which all contracts need, is the shopkeeper taking your money and handing you the goods (ie checkout counter). On the internet, the handing of the goods is the shipping - hence, no shipping, no acceptance, no contract, no Dirty Harry for a steal!