No, most of the web bots are trivially easy to filter out (the legitimate ones have identifiable signatures on purpose, the illegitimate ones usually don't behave like human beings), and the web stats firms do a decent job of that.Right.
Google Bots probably count for 50% of the traffic!
A lot of the problem revolves around what "a visit" means. (is a single page a visit? No, you probably hit a few pages on a single visit. How long a gap between pageloads -- or other type of behavior -- is necessary to qualify as two visits?... and so on). It's surprisingly hard to quantify, and there are no standards around it. Third-party web data sites like the ones Wasnex linked have to work from inference, because they're using data from third parties (usually ad providers, less frequently by tracker scripts the site owners installed on the data company's behalf, both of which can be defeatable by ad blockers, content filters, firewalls, etc.).



happens! 