Then we have the Mac, Linux and till a certain point Microsoft fanatics. They seem to have their fixed set of ideas and will leave no stone unturned in trying to teach the holy gospel. The Mac fanatic will not stop harping about how his/her Mac is the shiniest object on this planet and how they plan to donate a few thousand dollars to the Apple Foundation by buying more stuff from them. Then there are the Linux fanatics who cannot stop praising the good word of "Open Source" and how every line of code that is produced should be "Open Source" and how the latest version of Ubuntu is 100 times better than Vista or some such statement.
As for the MS fanatics I've not seen too many of them lately so cannot say much about them. Coming back to the topic when we move away from WFM to preaching that is when things become annoying. Unless someone really asks you for your expert advise please don't start up like a broken record. Let people decide what is right for them.