Cydoor is a banner service that Kazaa uses. It downloads ads and displays them in Kazaa, randomly replacing them and accessing the server for new banners. The only information it sends back to the server is a list of the banners displayed, the frequency of each, and any clicks to the ads. No information about the user's computer is sent or is available to the server.
Thus, Cydoor is annoying but harmless adware, not spyware. As I said, there are enough no-spyware guarantees on Kazaa's site and enough competent users around that if Kazaa did include anything that could possibly be seen as spyware there would be lawsuits galore by now.
Now, next time you want to call someone a pretentious retard, make sure they're full of shit first.
