If you've missed either of those, it's still highly likely that you've seen Russell Brand's public activism, as his speeches and appearances seem to be ubiquitous in the media right now. I've seen him on MSNBC, Russia Today, Fox (as an object of scorn), and of course the BBC. He shows up at Occupy Wall Street protests, gets interviewed by prominent British journalists like Jeremy Paxman and Mehdi Hassan, and is a frequent panelist for broadcast discussions of drug policy. Oh yeah: he does movies and standup too.
Why does he have such a broad audience? Quite simply, it's for stating the obvious; he articulately, passionately, accessibly, and entertainingly makes a compelling case for people everywhere to reject the pseudo-democratic oligarchy that's rapidly trashing our planet, hoarding our resources, and saddling us with massive debt.