I tried to use a gift certificate I was given only to find out that the seller required checkout on her site. When you do that PayPal will not honor eBay Gift Certificates.  So if you go shopping on eBay thinking you are going to use a gift certificate you are gambling that the seller will not require the use of a third party site for checkout. There is no way to know this until it is to late. If they do you loose! In my opinon this makes eBay Gift Certificates completely useless.