I'm not an expert of the sort that Edwin is talking about, but I do know enough to help out some newbies and I have posted a lot over the years. I've often asked myself why bother? (and I've taken time away of several months when I just didn't feel like being here).
I forget what it's called, but there's a theory in Economics along the lines of an "expert dilemma"
A nice discussion of this in Predictably Irrational by Dan Ariely. He uses the terminology Social Norms versus Market Norms.
Experts often get recommendations and referrals from the people they help.
I've asked a lot of the experts I've met at Pubcon and many moderators if they get any business off WebmasterWorld, and they've all said "little" or "none".
I think it's more like JDMorgan says - and both of us tend toward more technical forums, rather than the more theoretical SEO forums, so that makes us perhaps a little different from the norm here.
What attracts me to a question is:
- when it's something I know cold and can with little effort on my part help someone out. I've gotten some great thank you notes over the years and I really value that.
- when it asks about something I don't really know or understand and it gives me a chance to look into something I've never encountered, but might encounter some day.
- when it asks about something I think I understand, but realize that I would really refine my thinking and my understanding by trying my best to explain it as clearly as possible.
- the desire to be perceived as a contributor and not a freeloader, so that when *I* have a question/problem, I'm likely to get a response. I first started answering questions in the PHP forum for a simple selfish reason: I figured if I could answer some easy questions, that would free up time for the real experts to answer my somewhat harder questions. That paid great dividends.
There's an old saying: "To learn a skill, study it. To master a skill, teach it."