<p>+1 to all the answerers.  I think all of these reasons play a role for me--at least somewhat.  The one point I would like to make is how much I've learned from this site and the CV community.  Of course, I've learned a lot by reading questions and answers posted by others.  But, although I'm only good enough to answer the easy questions, I've really learned a lot by answering them.  Hunting down webpages and pdf's, looking things up in my textbooks, and figuring out how to explain something clearly has led me to solidify and deepen my understanding of these issues that I find deeply fascinating.  I also <em>enjoy</em> answering questions, and feeling like my statistical abilities and knowledge (such as they are...) are contributing something useful to the world in one more little way.  </p>
