Don't be afraid of "enforcement," be afraid of the site becoming low quality. When it comes to practical information, usefulness trumps inclusion in many cases. Think of the situation where you come to the site needing help with a problem. Do you want opinions and theoreticals (which you could get from random friends), or do you want practical advice from people who have actually taken on, and solved the problem in question?
Yes, we're all excited to be part of the beta, and yes we're excited to spread the word and get things going. No, we should not think that getting answers to everything is more important than practical information that people can use. If we find that too many questions are super subjective, we douse the same thingmechanism as appear in StackOverflow (or any other site): we vote down, we vote to close, we comment to give the OP advice, andwe suggest edits, we guide the community through example, and if necessary we vote down and vote to close.
I think now is the best time to set the tone. I really think we should do this. I do trust voting, but voting isn't culture - voting is a person's opportunity to vote individually. Voting is an individual voice within a community. Without a clearleading idea of what quality means, I fear it being watered down.
We should also remember that part of the purpose of the SE model is to make the internetsinternet a better place, not to simply create yet another community advice site without experts. The expert creed is absolute part of SE, and I think we should live up to it if we expect this site to take off.