The last time Google contributor got brought up, I mentioned I'd be happy to participate so long as I wasn't being tracked and could still block any remaining ads. As is, it seems that running adblock would prevent contributor from paying any of the sites I visit so I don't see the point.
I actually don't even run an adblocker any more - I just use a javascript blocker set for "default deny" which seems to work just about as well as a real adblocker.