The Real Player installer, over the course of maybe five to ten years, was so pushy about installing extra, unwanted software and sending private data that it garnered a reputation that caused people to be really careful when installing it, if they installed it at all. It is not really a perfect example for people actually opting-out, because I think one of the many criticisms was that it was often either not possible or extremely difficult to determine how to opt-out of its features (sending titles of files being played, annoying message center and ad popups, packaged additional software). That said, check out the Wikipedia page for further details.