I have had mostly successes with ebay, though I have never bought any craft or stitch item from ebay. I try to deal with the people who actually have "stores" on ebay, as opposed to just a person with some stuff they want to sell - if they go to the trouble of setting all of that up, then they will most likely follow through with the purchases.
I just don't think there's any way to be sure about ebay - you just have to pay your money, and take your chance, and if it doesn't seem kosher after about 2 weeks, then contact ebay and/or PayPal right away. I think I've just gotten lucky with the widely varied items I've gotten - I've only had one bad experience out of about 10 purchases. And that might be too many for some, but none of mine have been over $25.