In Area 51, the idea behind the Commitment phase is to gather enough committed people to reach a critical mass to insure that the site will be active and seeded with questions and answers for the actual launch.
For now we can only speculate how exactly the level of commitment is calculated, but it seems to be heavily based on the reputation of the users on the official SE sites. I can see how you could argue that high rep users are worth more than low-rep users. This doesn't seem to be a good way to handle this.
If I have understood the concept of Area 51, then it is to create sites for a community of experts on areas that isn't covered by the existing sites (SO, SF and SO). If the area is beyond what is represented at those sites, it seems like a bad idea to base the commitment level on rep level. The true experts that is needed to make the site great, might most likely be users with little or no rep.
A good example is Persian Information Technology and Computer, where the top rep that actually want to participate only has around 2k rep. It has gone to the extent, that the proposer has asked for commitment from high level rep users to help boost the commitment level.
This really beats the purpose of the of commitment, which is turning into sympathy votes.
I know area-51 is still in beta, but it seems like you should consider how the rep is calculated, as it clearly isn't working as intended now.