In the web/tech world (and many other domains), it seems the Big Ideas belong to the Young. Barely 27, David Heinemeier Hansson, creator of the Ruby on Rails framework, has changed the world and given the Ruby language a reason to live. Then there's Caterina and Stewart, creators of Flickr. And don't get me started on the creators of the blog service I'm entering this post in...Six Apart's Ben and