Would trading ads for bitcoin mining really be a bad thing? If the site (and the user) know what's coming ahead of time it's so much easier to contain; the main problem with ads is that they're completely arbitrary code that can't be verified until it's on the machine. Excluding people finding ways to hijack the ad and deliver malware, this seems like a much safer option.
Thanks to mattie_p for scraping my draft of this story off the forum and posting it (with some bonus editing as well). For whatever reason, I couldn't submit stories this morning.
I also think Tidbit is a cool idea, of course with some possibility of misuse. Will try to keep SoyLent posted if there are any developments in the court case -- which might turn into Chris Christie vs. MIT.