I've bought lots of fabric on eBay and have been very pleased with what I've received. In fact, I'm just completing a transaction right now for some Moda layer cakes. I've also bought charm squares and fat quarters. It's been a good way for me to get a collection of fabrics (especially charm squares) without buying a lot of extra fabric. Also, the fat quarter bundles were nice since I got the collection I wanted without a lot of driving and searching. I just make sure to add the shipping costs to my final price to determine if it's really a good deal. And I set a limit for what I'm willing to spend and don't go over in a bidding war.
P.S. That link didn't work for me.