When developing any application after you get the core built you begin adding features for the users. Typically you have to guess what would the users want and would use. This results in some features being essentially dead because almost no one ever uses them. There is no way to know what is *really* used V.S. what is used every once in a while.
With a web app:
- You can divide your customers in half. Give something a shot and if it works then role it out otherwise kill it.
- View the logs to see what page they leave one. Rework the text. Ad a link to the bottom.
- Follow customers through your sign on pages and see that 50% stop after page 2 and don't get to page 3
- Every page, every link, every action, even mouse movements can be tracked.
Compare this to desktop applicaiotn. Today you can only track the number of downloads or the number of CD's sold. Desktop applications need a way to log all of the user actions so that the developers can get reports about the usage.