I had an urge to implement something similar while ago using OpenID. Since OpenID authentication has a handshake between a content website and an identity provider, it would provide the perfect channel for handling accounting. Paying to read an article would be as simple as logging in.

It is undeniable that Google has enough gravity as an identity provider to encourage publishers to adopt such a model.

I don't really see how to get people to pay for an article sight unseen, though. Familiarity with content by known authors may be enough for some.