Justin worked (and still works?) on the Terrarium system and uses that experience as an example as he discusses various gaming topics in his blog… including yesterday’s post on creating random world content.
Generating random world content is one of those tasks that gets written off as a trivial matter. It isn’t hard to throw some stuff around a virtual space and call it good. However, after trivializing the world content generation during your first game, you’ll never make the same mistake twice. You should set aside quite a bit of time to think about your algorithms, employ consistency checks early on, and future proof your algorithms against later enhancements. Exactly how much time you should set aside is a project planning consideration based on how complex your world content is going to be.