it's just bots that work with your cookies and history, there's no people sitting on a pc looking at your traffic (well unless you live in the UK and you use some of those hot words
).
Facebook is a classic example of how these bots work: check out the publicity on the page, isn't it weird how they seem to know what you like? Whenever you press a "like" button on a page they store that info. The whole value of Facebook is the fact that it's the world's biggest database of customer trends and info, geographically, ethnically and socially arranged and to which people take part voluntarily.