What do you measure?
Measuring the number of users and revenue is OK for tracking the general growth of your web business but it doesn’t help you improve it. If you have 20,000 users in month 1 and 20,001 in month 2, what do you do with that information? You are still blind even though you have some numbers.
Posse tracks sales / user / month. If this number does not change after we have improved the product to make it easier to sell stuff, it would suggest that our changes were based on an incorrect hypothesis. If it goes up, chances are we improved the economic engine of the business.
If you choose the right few metrics, you can look beyond your own false (and expensive) assumptions to see what is actually happening.
What do you measure?