FYI, I've just implemented this
http://onestepback.org/index.cgi/General/CautiouslyOptimistic.rdoc. 
Let's see how long it might be effective. With this patch, pages with
previously valid links WILL NOT SAVE unless you uppercase the
protocol:// section of the link.  That'll be annoying for a while but
hopefully not as much as the spam (and hopefully this will have an
effect for a while).

The real-time blacklists and any other blacklisting measure seem to be
almost 0% effective.  Practically none of the spammers that have hit
us have been listed, and we can't keep up a manual list fast enough.

Next step is authentication.  I'm ready to put this one to bed.

-- 

Chad Fowler
http://chadfowler.com
http://rubycentral.org 
http://rubygarden.org 
http://rubygems.rubyforge.org (over 20,000 gems served!)