The Libraries & Information Science proposal currently has about 541 people who have committed to it. Unfortunately, only 81 of those people have more than 200 reputation on the site, so the site is stuck in the commit phase (for now).
This is going to be a bigger problem as more users start creating proposals that don't interest the majority of Stack Exchange users with 200+ rep, but do have a sizable audience elsewhere (the Chinese Emigration proposal is a great example of this). Those proposals are going to be stuck in the commit phase, where they will not have enough interest from experienced users, because the majority of Stack Exchange is interested in other things (such as programming).
However, a solution to this problem would be to ask some of the existing moderators on other sites to give these sites a hand for the first few weeks of their creation. They could educate the other users about Stack Exchange, and make sure the site is fulfilling the goals of Stack Exchange. By the end of the few weeks, the "normal users" should have enough experience to run the site on their own.
I think that this would be a much better solution than forcing users to register on other Stack Exchange sites where they don't know anything about the topic, and try to get reputation there (it wouldn't work, anyway).
EDIT: user badp pointed out that without experience, people wont be able to moderate a site successfully. There are a few solutions/alternatives that would solve that:
- Counting users as having 200+ rep after a mod has a chat with them in the chat room, and explains to them how stack exchange works.
- SE asking some experts in this topic field to commit to the proposal, and explaining to them how SE works. Then, those experts make sure the site does OK, and after the beta is over, they leave.
I think that it's a problem that area51 is limiting the sites that can be created to sites that interest people who already use se, which is mainly programmers. I don't really care how this is solved, but I think this problem should be fixed.
Edit (#2): Another option would be to start a heavily moderated private beta on the commit phase, and let users learn how to use stack exchange, and start getting an idea what the site is about. Once 200 people commit, the best questions could be migrated to the actual private beta.