Top Web Sites Running Linux

According to the tool I was

According to the tool I was using (netcraft) Amazon and Ebay could not be determined to be running Unix. Their status is simply unknown. If they are in fact running a flavor of Unix, I stand corrected, but your statement that "almost all top websites use some flavor of Unix" is simply incorrect, unless you are considering Linux a flavor of Unix, which I do not. Of course it is a descendant of Unix, but the point of my post was to show the popularity of this typically-free, open source OS, and how top billion-dollar web companies (like Google and Facebook) also rely on it (rather than paying for, say, Solaris, or some other Unix variant).