The whys and hows in handy FAQ format:
Three main reasons: In some discussions, there were too many people using the default "anon" as a "name," leading to confusion. As UH has gained more participants, we've picked up more nasty hit-and-run trolls. And we've picked up a new breed of spammers who took advantage of the anonymous posting ability to craft comments that manage to evade the site spam filters (mainly by limiting the number of links in their posts to one or two).
How do I register?
Go to the registration page and fill out the simple form (the toughest part is coming up with a Universal Hub user name). Hit Submit and look in your e-mail for a message from Universal Hub. Click on the link in the message, which will bring you to your new Universal Hub profile page, where you can set your own password. And that's it.
What do you do with my login information?
Your profile page will let you set a default so that you are automatically notified of any replies to your post. You can also "subscribe" to specific discussions (i.e., get e-mail notification when somebody posts there). You can decide, on your profile page, whether to let other users contact you (via a Universal Hub form; your actual e-mail address never appears, unless you type it into a post or comment yourself). Other than that, I don't rent or give out e-mail addresses. I do occasionally contact individual posters if I have a question about their posts.
Feh, I don't trust you to keep my info private.
That's your right. I've been doing online stuff in Boston for years and years, so I do have a reputation I'd like to protect, but if that isn't good enough, you can create an account at some Web e-mail host, use that to log in here, then delete that account (the danger there is that if you forget your password, there won't be any way to have a new one sent to you). I am working on enabling OpenID (I'll certainly post when that's available). If you happen to have a drupal.org account, you can use that here.
Won't this new policy inhibit some discussions?
Quite possibly, and it's one of the reasons I dragged my feet for so long on requiring registration to comment on posts (the other involved some technical issues). But I think we've gotten to the point where the problems related to a completely open system (see the first answer) are beginning to outweigh the benefits. I could be wrong; I'll certainly be watching to see what happens and could reconsider requiring registration.
Any questions I didn't answer? Reply here or e-mail me.