Tidbit - a node knockout experiment; site visitors help mine bitcoins.

This a node knockout entrant (not by me) that I found super-fascinating, particularly because of its pitch as a monetization alternative to advertising.

There are a lot of issues the creators haven't addressed yet: opt-in, preventing user experience / performance from suffering, what's the actual amount of money you're making from traffic compared to ad revenue, etc.

But I think the concept has potential, and wanted to show HN.