The money's good. But PayPal uses real dollars. And now, instead of just techno-nerds, the service is attracting mainstream users. Registered users can send a payment to anybody with an e-mail address just by writing a dollar amount into an online form. When the e-mail is sent, the payment is charged to the sender's credit card or bank account.
Registration takes five minutes.
Completing the form also registers the receiver as a user. It's easier than catching a cold. And it is spreading as fast as a virus. Taking the money out of the system isn't as quick. But the big fans of the system keep the money in their accounts to use again.