Odds are, unless you regularly run anti-Spyware software, your computer is full of it. Not only does it invade your privacy by hijacking your web browser without your knowledge, throwing up pop-up ads, and reporting your activities to companies, it can slow your computer down and make it unstable.
This article as Joeuser.com talks about the growing problem of Spyware and how, thanks to legitimate companies bundling it and distributing it, it is financing a whole new Internet business model at the expense of unwary users.