Matt Haughey has a good rant on why, from a buyer's standpoint, Paypal is a great way to buy things online.
I'm lazy. If I want to buy one of your custom shirts off your site using paypal, it's about three clicks and a quick login that my browser already knows. It goes like this: 1) I want it! 2) hit checkout 3) login and 4) paid! It doesn't matter if I have money in paypal or if it just gets pulled from my credit card on file, it's still just a few clicks and I'll have a shirt in tomorrow's mail.
When I hit a full-on shopping cart payment system, I see forms and forms mean tedious work, and I know I have to dump my credit card into yet another database that I blindly trust won't get compromised anytime soon, but mostly it's the work involved that diminishes my impulse buy.
