Where do the "user123456" names come from?

Question

I'm new to Super User / Stack Exchange and I like it so far. I've noticed a strange trend. There seem to be a lot of new users in the format of "user132456" the numbers being random. Are new users auto-assigned this until they get some rep? Some examples being

Removing Facebook and Twitter components from OS X

how can I add a path permanently

etc. I'm mainly just curious.

Answer 1

If you don't choose a user name, that's what you're assigned: A unique ID, which is increasing with every new user, of course.

Here's what you see if you're not logged into Super User. You can post questions or answers without signing up, and without the need to choose a user name.