A large portion of this is dependent on the software stack you end up working with and the associated communities. The Ruby on Rails and javascript communities

A large portion of this is dependent on the software stack you end up working with and the associated communities. The Ruby on Rails and javascript communities heavily advocated open source work so many developers have open source work and/or a blog. Then you look at .Net. The amount of open source work is significantly smaller. Most software stacks have communities somewhere inbetween