It's really not prudery that's to blame. It's the high rate of chargebacks that come with adult material purchased online. People who buy access to porn sites later regret the purchase, especially if their wives see the charge on the bill. So they claim fraud and get a chargeback. This happens to Visa and MC, too. (Which is why DAZ can't accept those cards for annual PC memberships.) But Visa and MC also have tons of non-net transactions to help keep them afloat - all the purchases made at brick-and-mortar stores. PayPal does not.

Basically, any online pay service faces the same problems, so do not expect any PayPal alternatives to be any better. At least, not for long. They will either have to adopt policies similar to PayPal's, or they will go bankrupt under a flood of chargebacks.