You need to look at the main page of the listing, as right under the name of the item will be listed who is selling it. Different sellers offer different levels of quality of service. Whenever possible, I try to buy items that are both *sold* by Amazon and *shipped* by Amazon. It makes returns really easy. If Amazon is not the seller, then I check the seller's feedback before deciding whether to purchase.
Also, I believe Amazon bought fabric.com some time ago. One of the QB posters mentioned seeing the same fabric on both sites. Since fabric.com offers free shipping with orders of $35 or more, it's always a good idea to check Amazon fabric against fabric.com . I usually also check eBay and bugfabric.com (they carry a lot of older lines of fabric).