A Q&A site is not a piece of legistlation; it's an entreneurial endeavour.

It's best to leave entrepreneurs to be free to create, experiment and adapt.

Stackexhange will miss out on some great sites by rejecting them before they even get a start. The best sites will be those where the founder/s constantly adapt the site to demands of the community, not those who have the best idea upfront.

But as you say, that's where the OSS optios come in. :)

And just look at how many crap blogs are on each of those platforms. Their goal is to curate quality content and the free-reign model has already proven itself to be incapable of it.