It only takes a couple of minutes to register a name. If you allow a cookie (optional) you can also have the site log you in automagically. If you don't allow the cookie, you can still use the forum and the username, it's just a pain in the ass having to continually log in. That's not something I set up intentionally, it's just the nature of the beast.
Now, all that said, there are a couple of really nice benefits to having a registered username. You can use the PMs. You can watch topics so that you get email whenever that topic gets a new post. But most of the benefit goes to the readers. It just gets confusing having a conversation w/ a bunch of different anonymous people. You can never be quite sure who said what or even how many different people you're talking to.
Admins and moderators (including yours truely) have a slight advantage in that we can see which IP address each post comes from and it comes up in a tidy report showing all posts from the same IP. But that doesn't help much where more than one person is using the same proxy (as w/ default AOL behavior)
Just some factoids.... pretty sure most of this is in the FAQ already.
Here's freedom to him who would read;
Here's freedom to him who would write;
None ever feared that the truth should be heard,
But them that the truth would indict.
--author unknown (circa 1914)