I'm a co-leader of our local PASS chapter and also on the committee to host our first SQL Saturday in spring 2010, as well as a member of several local civic associations.

Yes it takes time away from the family. But I find I get always get back more than I give by meeting new people, making connections to people and orgaanizations, and learning from others. Also as Brad said there is lots of opportunity to develop and hone new skills. You can work on things you may not think you are good at, like public speaking, finding sponsors, etc and develop these skills with the help of others.