The major problem with financial transactions is that each country (or I guess, _most_ countries) have different laws regarding banking, fiduciary responsibility etc.

Paypal/Amazon/GCheckout work globally because they use CC and charge handsomely for the privilege. Companies like Pin, Stripe and Dwolla are trying to cut out the idea of merchant accounts (which create the major hassle for a lot of small practitioners), but that means tailoring your service for local laws = hard problem.