According to Netcraft, the non-commercial distributions are growing faster than the commercial Linux distributions. In my opinion this is not a big surprise, but with the major companies aquiring some linux distributions like Novell with SUSE, the companies which have partnerships with Novell or Redhat will maintain or migrate for these commercial linux distributions.
Debian is currently the fastest growing Linux distribution for web servers, with more than 1.2 million active sites in December. Debian 3.1 was declared stable in July and it appears that both the anticipation of this release becoming stable, and the release itself, have generated new interest in Debian, after some years where it had lagged behind its more active rivals. This growth is particularly noticeable at some of the larger central European hosting locations, including Komplex, Lycos Europe, Proxad and Deutsche Telecom.