I don't think the email confirmation was slowing any spammers down, frankly. It just caused more problems for legit people. There were already dozens of new spam accounts coming in every day, it's just easier to see them now since they're now included in the log.
The most effective thing so far was putting the page title blacklist in place, which blocked over 90% of the spam pages. I'm ok with the spam accounts being there if they're not actually creating spam pages. And the ones that get created are rarely linked to from any of our pages, and I try and get them cleaned out every day or so.
I've got a "watch" set up on the Main Page as well so I get an email whenever it is edited.
I'm satisfied with how things are currently working.
From: Code for Libraries [mailto:[log in to unmask]] On Behalf Of Daniel Chudnov
Sent: Sunday, February 10, 2013 4:13 AM
To: [log in to unmask]
Subject: [CODE4LIB] wiki / spam
A look at recent changes reveals a lot of suspicious looking accounts and some suspicious activity.
I understand Ryan's urge to disable email confs for sign ups, but perhaps avoiding defacement is a higher priority, especially right around a conference event?