I think Twitter and Facebook are great ways to reach out to potential new members. There is really no negative to spreading your information across various platforms.
I get all my clients on there, with at least a minimal presence, because Twitter, Facebook, and YouTube are used as Search Engines by a growing demographic... youtube was actually #2 in total searches last year to Google at one point.
So when a person who uses those mediums (and that number is in the billions) does a search for a Toyota Club, you want to to come up, even if you don't "do" a lot there, you point folks to your website, or your forum (here in our case) and you've "caught" them.
The best part? It's free. There's literally no downside to spreading your message to millions of potential interested parties.