A great idea from the folks over at 37 signals.
It’s easy to think that the relative-time style of “this comment was written 15 minutes ago†is incompatible with caching. How are you supposed to cache something if the text changes every minute? Static pages with JavaScripts, that’s how!
Update: Looks like this type of idea has been around for a while (I’d just never thought of it before)! 
