"If I remember their argument correctly, cells that "only" reproduce anarchically present little danger (benign tumor) if they don't also do so at an abnormally fast rate / metabolism."

Forgive this (very tortured) analogy, but I think there is a lesson here for would-be extropians who think society will simply tolerate a few vampires here and there.

Specifically: they'd better be living lives of quiet, impoverished contemplation ...