I'm on vacation, so I won't digAfter digging into this right now - maybe someone else willa bit further, else I can revisit it when I get backcan't find any conclusive evidence that this has really helped much.
But here's a little bit of info: inIn the 60 days prior to registration being enacted, Programmers got 877 bad* questions from registered users, and 182 from unregistered users, making up 48.05% of those asked by registered and 76.15% of those asked by unregistered users respectively.
In the past 60 days, Programmers got 13141221 bad questions from registered users, making up 5455.32%53% of the total asked. There are some holidays in there though, so that doesn't really tell the whole story. Here's a picture:
Interpret that
What I didn't see (but hoped for) was a significant drop in the number of questions asked. So far as you willI can tell, the folks asking crappy questions with unregistered accounts just registered their accounts and kept on a-goin' - the number dropped slightly right after the change went in, but then went right back up again.
It probably improved the effectiveness of the quality ban slightly, but you're not gonna see this reflected in account deletions, and I'm not gonna talk to much about that anyway. But, here's a picture for gnat:
The best reason for doing this is probably just the slight bit of extra resistance it provides, and the somewhat fewer headaches involved in having registered accounts (both for the asker, and the folks interacting with him). I wouldn't turn it off again, but I wouldn't encourage sites with less traffic to enable it either.
As an aside, we're working on changes to the registration system that should help to encourage folks to register their accounts without requiring it - this should ease the transition elsewhere.
*closed, deleted, or down-voted below 0.