Even though I'm not an admin, I'd like to offer some ideas on the matter.
The major idea I have would offer a modicum of security: Wikipedia sets up a POP server for admins and the admins have their e-mails run through the server. Their personal data, such as their name, is scrubbed if the Admins wish it -- leaving only their handle on Wiki. Changing code a bit could, theoretically, screen their IPs so they were only visible to admins or higher -- thus eliminating one method of tracking them down.
Unfortunately, the rest is up to the Admins themselves. You can't stop someone from collecting data about you that's freely available unless you have evidence of malicious intent -- then the law can offer you protection. Of course, in theory, a court order would shut down his website if it could be proven that his actions were promoting illegal actions such as threats. But again, legal actions are something you want to save as a last-ditch effort since they take time and money and create a lot of publicity.
I don't know if this helps or not; I'm just a year-old editor on the project who is concerned for the safety and security of all involved. Brandt does not seem to be someone who has anyone's best interests in mind but his own.
--Martin Osterman