That would defeat the entire purpose of "commitment." The goal of commitment is to find people who will actually show up on opening day, not just to find more people who will click on a link.
Starting a new site is hard; Pushing a site through commitment is supposed to be hard. If users can simply commit to everything in sight, all we would end up with is a significant decrease in follow-through, resulting in more failed private betas.
There are a lot of fans of Stack Exchange (in the abstract sense), many of whom are more than willing to say "Yeah, there should be a site about…", but very few who will actually show up to the private beta once the site is created. That's when we need them.
A Better Solution is on the Way…
We will be adding adding a reminder email to let followers and committers know when a proposal has reach 60% and again at 90%. If you follow a proposal, you will receive notices when the proposal is much more imminent. That's when it is time to tell your friends and commit the the proposal so you get an invite to the private beta.