It depends on your demographic. I use Amazon FPS:<p>- because my customers will probably have an amazon account w/ CC info in it, and will probably not have a paypal account.<p>- to avoid having to deal with storing CC info on my end.<p>- to avoid having to buy a HTTPS cert entirely.<p>That being said, I am not huge on the fact that they leave my site to go pay -- though, I'm hoping users are used to this by now (a la paypal).