I purchased a "used" copy of QuickBooks Pro for Mac on ebay, under the impression that it was unregistered.  When I received the product, I tried to register it, but it had already been registered to another company. I called Intuit customer service, and they informed me that it is illegal to sell a product that has already been registered, and that I would have to purchase an additional license for $299.00USD to register it. (That's the price of the QuickBooks Pro for Mac 2007)

If you are purchasing any type of software, please be sure the auction states that it has been unregistered, or email the seller and clarify that it has not been registered. The software can be listed as "used" but can also be unregistered. If not, it is illegal for the item to be sold.