There are two very simple reasons why paypal is used by vendors, sometimes only. The first is cost. Merchant accounts -- which are needed to handle credit card transactions -- cost money to set up. While 100 to 150 (on the low end) isn't a great amount for some, it's only part of the costs of operating with such -- not something that a smaller site can easily do until they've established themselves. The second is acceptance. Despite the horror stories, paypal is the single most widely used and accepted form of payment on the internet. It exceeds even credit cards. And, since US Custoemrs don't need to even have a paypal account now to use the paypal system to make a credit card payment, they make it much easier for smaller merchants to get in there. I've read paypal sucks, and most of the time, the issues come from not paying attention to what they were doing and what they were dealing with. Paypal is not a bank, does not have government oversight, and has few effective competitiors. In fact, within the US, they have no effective competitor. As for how roisty keeps their ability to use it, well, it's either the whole membership thing (can't see bad stuff unless you are a member), the volume of money (paypal gives them a bye 'cause they make a lot of money), or no one's complained yet.

thou and I, my friend, can, in the most flunkey world, make, each of us, one non-flunkey, one hero, if we like: that will be two heroes to begin with. (Carlyle)