I have a couple of domain names and 3 blogs. The latest is samwize.com.
The first domain name I bought is just2me.com, on the Christmas of 2007. It's powered by (Google) Blogger. Since then, I have wrote all kinds of entry on it - development stuff, work, new apps, personal life, etc..
Then in May 2009, I bought just2us.com. I thought I should split posts on personal life with rest of everything. And I like to try out Wordpress, which is more customizable. Of course the domain is a complementary. Things for me, and now things for us.
Fast forward to now, in Sep 2012, I bought samwize.com. The reason is that I want to try out Octopress, a blogging framework that let you concentrate on writing. I have also wanted to split development guides with rest of everything (like apps and news) in just2us.com.
What's more, every good developer has a personal domain name.