As someone I know has put it, "...given that Reddit says that it views itself as a government for a new type of community, this is disturbing."
I'm going to make some unfounded but logical assumptions about you. I'm going to assume you're a nerd or at least semi-geeky, because you use slashdot. Next, because of the previous assumption, I'm going to assume that many of your friends are geeks or nerds, and you generally hang around like-minded people. This sets your friend group in a niche. In this niche, there is probably a much higher probability that these people have opinions on technology and like to educate themselves about what is available, as it's logical to assume that a nerd or geek finds technology to be something of a hobby, and people tend to know a lot about things they consider hobbies.
Taking all of this into consideration, I'm going to assume that there is a higher likelihood of people in your friends group who want to put forth the effort to change operating systems on a computer or laptop or netbook, simply for the sake of exposure. So already we've assumed that the people you are friends with are more tech savvy, more opinionated about technology, and therefore more likely to try linux or whatever is out there. So within your group of friends, a percentage of even 20% that use linux would not be surprising. However, much like unscientific pools, it is an inaccurate measure for the rest of the uneducated, uninterested majority population that could give a crap about what their computer is running as long as it does, even with much difficulty (adware, spyware, malware, viri, popups, toolbars, etc), what they want it to do.
But it does move! -- Galileo Galilei