http://www.freebsd.org/doc/en_US.ISO8859-1/books/handbook/nutshell.html#introduction-nutshell-users You also forgot some biggies, like Netflix, oh and Apache themselves. Sampling an OS's usage numbers off of how many public facing web servers are out there will give you very biased results. I have two FreeBSD servers running OpenBGPd and OpenOSPFd, and two that are NFS servers, there is absolutely no web server on them. They are ROCKS of stability. This is just FreeBSD, a partner ISP I work with runs OpenBSD route reflectors.