I purchased some yardage for a backing last year from a seller in Canada. I assumed it would be a shade different than pictured, which would make it perfect for my needs. Bought it for a fair price, it arrived in 5 days....and was exactly the color the picture had showed. I used it, but not on the quilt I had intended it for.
My first purchase on eBay was for 100 5" cotton squares. I expected a large variety of fabric patterns and shades of blues, but there were only about 10 patterns and more than a quarter of them were thin gingham or see-thru fabrics. Watch out for those kinds of packets.
I most certainly will continue to buy fabric on eBay, but I'm careful at reading the descriptions, I pay attention to the seller ratings, and I don't hesitate to ask the seller any questions I may have.