It looks as though this site is not able to track individual people, but only companies. I'd guess they're doing this by querying each visitor IP with a database of known IP addresses used by companies. If so, it's not particularly sinister, not particularly useful, and not particularly accurate.

The discussion being had here - http://news.ycombinator.com/item?id=4891637 - deals with a site that is allegedly identifying visitors individually somehow, most likely through something to do with social media. However, I'm skeptical.