Link to actual content rather than reddit post:<p><a href="http://blog.joa-ebert.com/2010/08/19/introducing-jitb/" rel="nofollow">http://blog.joa-ebert.com/2010/08/19/introducing-jitb/</a>
I wonder if it's fast because it's incomplete, and when you start adding all the harder things - and especially the special cases, you realize things are more complicated - and slower - than you thought.