The way I understood the scam to work, is that the check IS real, only the check is from some poor sucker who is just trying to buy something that doesn't exist.
For example, africa dude lists a fancy milling machine on Ebay and tells the buyer to send the money to HDTV dude as if HDTV dude is the seller of the milling machine. That way, the check gets cashed by the innocent HDTV guy and the resulting money is sent to africa dude. The person who wrote the check is the guy who gets burned.
I once sold a desktop CNC milling machine on Ebay in the neighborhood of $3300 and the buyer sent a money order! I was amazed at how easy it would have been for me to just burn the guy. Of course a huge paper trail would be left behind, but for a junkie who just needs to get high that would be the least of his worries.
--Dan