Linking Categories

Okay a few questions..

1. Is there a way to limit the amount of sites a person can create (rather than the unlimited amount of sites)? If so, how would I go about doing this?

Okay 1 was a little more simple and easy but this next question is a little more complex. Hope you can help thanks so much!

2. I figured out a way to create the same categories on others pages when they create a site. Now is there anyway I can take feed those categories to the categories on my main site? For example if I create a category called “Food” on my main site and you register blog off my site I have programmed it to make a “Food” category on your blog. Is there a way I can take whatever you post on the “Food” category on your blog and have it feed to my “Food” category on my main website, and for every category I have and every user and blog on the network. Even if I have to manually set this up on each individual blog on my network that is fine. I am willing to do that.

If you guys can help that would be amazing.. thanks so much!!!!