Well, if you thought their previous post title didn’t let you know what they were up to, their latest one definetly will as WordPress.com adds domain registration and mapping for your blog.
Hate being guywriting.wordpress.com, register coolguywriting.com through their interface under Options -> Domains.

It’s here: you can now use your own custom domain with your WordPress.com blog. For example, if your blog was currently at example.wordpress.com you could buy example.com from us and we would automatically move your blog over and redirect all your links and readers to the new domain.
How does this work? Well to get started go to Options > Domains. You can enter the domain you want in the box at the top. Enter the domain you want.
If the domain isn’t registered, it will ask you for some information and then register it for you, and add domain mapping, for $15/yr.
If you already own a domain you registered somewhere else, you can map it for $10/yr.

Domain mapping service is a bit more expensive than I had hoped, but still reasonable enough that just about any of us can use one of our Godaddy domains sitting doing nothing and use them for our WordPress.com blogs. I know many people have been waiting for this functionality, and if you consider the fact that they give you the domain registration and the domain mapping for $15 a year that’s a pretty good bargain in my mind.
I think many of users will be willing to fork that over. Hopefully the WordPress.com crew will use any small profit they make off the deal to continue to add new improvements to the growing service.