Epiphenomenalogy is essentially unknown outside academic philosophy, and now the lesswrong readership.

I'd say it's more widespread than that. Some strands of Buddhist thought, for instance, seem to strongly imply it even if they didn't state it outright. And it feels like it'd be the most intuitive way of thinking about consciousness for many of the people who'd think about it at all, even if they weren't familiar with academic philosophy. (I don't think I got it from academic philosophy, though I can't be sure of that.)