If we were to go forward with something like this, should the ladder be 2v2 or 3v3? I think 3v3 is more fun but it would be easier to for people to be able to show up and play 2v2 (and to find a partner for it). A roster of 4 people should be enough to field a team for 2v2. Perhaps there would also be interest in having a 1v1 ladder. Aside from finding a place to set up a ladder, we would also need to have competition-grade custom maps.
Some possible ladder sites:
Clanbase -- http://www.clanbase.com
Team Warfare League -- http://www.teamwarfare.com
Online Gaming League -- http://www.worldogl.com/
Maybe it would be best to start informally and perhaps to arrange things at the [DT] forum where I can keep track of stuff. Our forum is at http://SinsDreamTeam.yuku.com