Today's great post if by Fred Wilson titled titled Venture Fund Economics. 

"When I write about venture fund returns, there are always comments and questions that lead me to believe that the economics of a venture fund are not well understood. And since most of the readers and commenters on this blog are people who work in the startup ecosystem, I think its important that the economics are better understood. So I am planning on some posts on this topic in the coming weeks."

This appears to be the first of several posts Fred's planning to write on this topic. I'll try to remember to point them out when they appear.