Every board, thread and CH poster, # of posts has a # attached. Boardreader stats change all the time. Domain sites provide background as well. Owner sites have one sheets with press releases on such information.
More than 2 million registered subscribers, no idea how many are active (since s/n's aren't deleted even when a known CH has passed away-kinda sweet isn't it).
Is the Recommend button a feature a "lurker" would use over typing a comment?
As long as we're asking questions, I'd like to know how many of those accounts are active posters, how many are mostly lurking and how many are inactive. I'd love to see a graphic of posting activity over time, but I would think that would be the sort of thing TPTB would prefer keeping for themselves.