Tells owners of the website how many people are visiting the site, where they are coming from and whats most interesting to them.
http://wordpress.com/features/stats/
Analytics and Tracking · Audience Measurement · Visitor Count Tracking
Get access to data on 1,058,162 websites that are WordPress Stats Customers. We know of 42,420 live websites using WordPress Stats and an additional 1,015,742 sites that used WordPress Stats historically and 27,333 websites in the United States.
Get a list of 1,058,162 websites using WordPress Stats which includes location information, hosting data, contact details, 42,420 currently live websites and an additional 12,911 domains that redirect to sites in this list. 1,015,742 sites that used this technology previously and 27,333 websites in the United States currently using WordPress Stats.