[techjamie]

I suppose in my case, both? I use my first name everywhere, but keep my last name private.

The theory behind it is that my first name is common, and having that one common element shared between so many people that make usernames creates a barrier to gathering information easily. If my name was too unique, then it would be easier to find and identify my activity, but as-is, I am not the only person on the net with my username, so anyone performing research has to spend extra time weeding out those people.

Also, I generally don't post anything I wouldn't stand behind anyway.