Our payments for subscriptions runs through an automated e-commerce system which relies heavily on PayPal. PayPal handles the major credit cards for us and subscribers in the developed world can join in with little difficulty. PayPal does a good job for us. The list of countries where PayPal works looks impressive, but note that for many of them one can only send money.
There is a problem for many readers in countries where PayPal purchasing is not supported. We have been selling Le Monde Diplomatique like hot cakes in the last two weeks, and we would be selling many more hot-cakes if PayPal had complete African coverage.
We would be very interested to hear about alternatives. But I suspect that there are no easy answers to this question and a large part of the problem is that many of the countries where the PayPal writ does not run are under restrictive foreign exchange controls; government control is the underlying issue. Getting a decent global infrastructure for web-based e-commerce is not a shoe-in.