I was listening to the most recent Distrowatch OGGcast http://distrowatch.com/podcast/dww20070910.mp3
and the host brought up an interesting question, why does Ubuntu win all of the polls? Well here are my reasons why the next top competitors aren't on top.

Suse (SLED and OpenSUSE): No one trusts Novell. People tend to switch to Linux to get away from Microsoft, so why use a partner's distro?!?

Mandriva: I think Mandrivia is just crap, they focus way too much on the "club" (the tossers that actually pay for it) and don't focus enough on community building.

Debian: scary server OS