I participated in a lunch meeting recently with a number of people from MS that work on their community efforts, and I thought one of their questions was interesting, if obvious; what do you get out of participating in the community as a speaker or group leader?
I think it falls into three buckets:
For me the first two apply. I do a one minute bio that includes what I do for a living and that's the extent of the sales pitch. Over time I hope to earn karma that comes back in the form of students in class. Just as important for me is that I enjoy helping those new to the profession grow, mainly because I see how much faster I could have grown if more help had been available/offered.
Nothing wrong the the last one, everyone reaches the point where they want validation - to prove to themselves, or their boss, that they are somebody. MS has accentuated this one - successfully I think - by making many of the community leaders MVP's. So part of this loops back to indirect marketing, hoping that listing speaker/community leader/MVP will lead to increased business (and I'm sure it does to some degree). The only downside to this one is that some point I think you should move past validation and move into the zone that only time/experience can bring - nothing left to prove.
I'm reasonably stubbon about my approach; I do the things I enjoy/want to do without worrying about the ROI. Not everyone can afford to do that, or would want to adopt such a karmic approach, but it suits me and seems to have worked so far.