I do know about the participation thing from my experience as a programmer: back when I spent lots of time participating on forums answering questions I would get occasional job offers come in from people that know you just because you're always around. Since I've moved my spare time from programming forums to writing (and writers' corner
), I no longer see such offers come in. Basically: you've got to be seen in order for people to remember that you exist (which, I guess, is the other side of: out of sight, out of mind).