Web analytics is very common and it is used to learn more about the user experience of your website. It provides useful data such the number of visitors, or the most popular page.
However, I am also interested in learning about how I communicate via email. For example, it would be interesting to know how much email you receive per day, or what proportion of emails you reply to.
This can also be applied to reading RSS feeds. Google Reader already has a useful feature that shows you various statistics on how you read your RSS items. Another interesting application would be in phone calls.
