I've been doing web dev for over 8 years now and only since starting work at an agency have I signed up to github (about 5 months ago).
When you working on a project with multiple people then some sort of git of svn repo is almost c must. Hard to work without.
The fun starts when you get conflicts

@Everyone Else: Ive asked deus-ex-machina for some help with a feature on a site a few friends and I are working on, hopefully sometime in the near future i'll beable to pass on some positive feedback