If you're already a Linux user, it's sometimes hard to believe that not everyone knows about Linux. Just read the tone of this article from the New York Times, and you'll see that this is changing slowly but surely:

"The Linux operating system, created by Linus Torvalds in 1991 and improved by countless programmers over the years, has been traditionally used for heavy-duty computing tasks because it is usually much less expensive to set up and operate than Microsoft Windows. Linux can run on the same PC hardware used by Windows."

Well, that paragraph doesn't really make a lot of sense to me, but I guess that's what it takes to get it into public awareness.