[jerf]

By the time you're done manifesting that concretely, you've nearly got Patreon. Yes, it's not quite identical, but, for instance, once you accept that the site still has to opt-in it ceases to be magic.

[icebraining]

Or Flattr.

[nailer]

Or window.payment which Chrome and Safari are already implementing (using Apple Pay and Google Wallet respectively).