Fred Wilson has today's great post up titled Portfolio Screens.  This is the second post that describes how Fred is thinking about his portfolio right now and follows another great post of Fred's titled The Survival Matrix. 

The size of the balls represents the amount invested in each company (the picture above is of a theoretical portfolio.)  In Fred's world view, he wants to "see the balls move up and to the right over time. And you want to see them start out small and get bigger as they move up and to the right."