I posted this question at the Village Pump last night, but it hasn't got much response (perhaps because most everyone was asleep at the time I wrote it).
http://en.wikipedia.org/wiki/Wikipedia:Village_pump_%28policy%29#How_many_Ar...
The crux of my point is that the number of active editors in Wikipedia has grown nearly 10 fold since ArbCom was created 2 years ago, while the number of Arbitrators has remained constant at 12.
Perhaps this just means we should expand the pool of Arbitrators and elect 20 or 30 this time around as some people had proposed (though one might have trouble finding enough people to run).
As an alternative, I suggested moving to a system more like Admins / Bureaucrats where we continually approve trusted members of the community to serve in this role and allow the pool to grow as needed to keep up with Wikipedia's growth. A pool of 50-100 trusted community members, working in groups of 10-15, could make short work of the backlog generally seen at RFArb.
-DF