Homebrewing for me is much more of a lifestyle than just a hobby, and I'm sure there are lots of others here like me.
+1 It's shaped my outlook on a number of things, particularly the DIY mentality with regard to food/drink. Also, the science behind brewing has shaped my understanding of food chemistry and other natural processes. As for social aspects, well, homebrewers are pretty much some of the nicest people you'll meet. And I've found that homebrewers are a knowledgeable bunch on a wide range of subjects.
I was just saying to my wife that I started homebrewing 13 years ago this month. I still remember the excitement I felt reading my first homebrewing book. Now, I'm on the Governing Committee of the AHA. Today, I'm going to the state capitol to get my picture taken with the governor as he signs our new homebrew legislation, the most liberal in the US, which I'm proud to have had a hand in. By the end of the week, I hope to find out if an offer I've been made for a homebrewing book will go through. It's a hobby that's gone farther for me than I ever thought it would. Definitely it's shaped my life for the last 13 years.