I watched Scot hanselmann's presentation at mix '10. When he presented the tiny urls for Nerddinner he said it was a 2 part process.
a) modify global.asax.cs with a new route b)some sort of isapi rewrite.
When I implemented this in my asp.net mvc 2 site I only did part a. and it works. why then did he do part b?? what is the advantages of doing that???