I'm not sure how we missed this when it was released a couple of years ago but there's a short documentary film on baseball card collecting called 'The Last American Hobby'.
Samuel K Day, Ethan Edelson & Alberto Peart produced the film, which includes interview cuts with Alan 'Mr. Mint' Rosen, a few hobby shop owners and a collector or two.
Unlike a lot of television segments on the hobby, there's some depth to this one, which starts out with a sort of dire lament about the death of collecting but rebounds nicely over the last couple of minutes to show a successful shop owner turning kids on to cards by holding in store games and contests and inviting local Cub Scouts into his store.
The Last American Hobby is well done and well worth the five or six minutes or so it takes to watch. Here's a link: http://www.ethanedelson.com/gallery/The_Last_American_Hobby.html