An interesting article at Ars Technica. Well worth your time.
A listener wrote in with a series of related questions after last week's show and I'm actually doing something of an investigative bent to answer then and present what I find on the show, either next week or the week after that.
There is an awful lot of deception in software. Especially in freeware supposed to enhance security. Bundled toolbars with absolutely no notice to the user is probably the most common fault. But there are too many to count. Really.
At any rate; this is a pretty good and fairly concise overview of the problem.