Not to be an a&& but unless they used a 0 day exploit, which is doubtful because all of the possibilities I see are at least a month old, it is the administrators fault.
Now don't get me wrong I realize this is probably not a full time job for JJ and just a hobby, but don't compalin if you are rooted because you did not patch it is your fault.
Let me say that I think this site is great, easy to navigate and informative, and I think JJ has done a great job with it.
Just some questions for JJ.
Did you just replace the page? (if that is all you did, you should really check all users accounts to make sure none were added, in addition you should check all running services to make sure none were added).
For your reference here are links to the two vulnerabilities I think could have been used to root your site: http://www.iss.net/security_center/static/9249.php http://www.iss.net/security_center/static/8308.php
Just so you know it is really easy to find out what a site is running I ran a query on netcraft.com and this is what it told me about your site:
Just trying to help.