I would much rather have a name than a URL, even though the URL is a good thing, because it's how the network gets its loose-coupled-ness. It tells anyone who cares how to find the new stuff from me. It's stood the test of time, it works, it scales reasonably well, and it allows choice. The only thing wrong with it is that it's ugly!
1. If you don't already have a domain, and most of us don't, you can go to a registrar like GoDaddy or Gandi and buy one. But most people won't do that because you will also be able to go to providers who will sell you a sub-domain much more cheaply if not give it to you for free. It'b been argued that it's too hard to get a domain or a sub-domain, but it doesn't have to be that way. There's no reason it should be any more difficult than getting a username on Twitter or Facebook. All you're doing is associating a string of characters with an email address. There's nothing hard about that, not in 2010.
2. When you register the name, if you already have an RSS feed you want to be associated with that name, as I do -- you'll just enter it into a text area on the registrar website and click Submit. Then the URL will be stored as the TXT attribute of the name and served up to anyone who wants it over the DNS protocol.
For example, my name would be davewiner.com (I already own that domain), and the associated URL would be http://scripting.com/rss.xml.
Now you could imagine a special TLD, something like .rss, that would be understood when you enter a name. I could register dave.winer.rss for a nominal charge, and if you want to subscribe to me, you could enter dave.winer. The .rss part would be assumed, just as .com is assumed in a lot of contexts on the web.
See how this is working? Everything in this space seems to involve URL-shortening. This is no exception. And this is as far as we want to go, because now the name is as short and as easy to sign up for as the centralized networks, without the centralization penalty.