User created sites within Multisite?

Hello.

What is the best and most secure/robust way of setting up a multisite network where users can create their own sites?

Obviously once logged in they can, give the site a name and a domain my domain.myblogs.com (if available) etc.

I think BuddPress does something similar to this, but wondered if there was a better way. A nice signup form, clear insturction etc.

Also each user is limited to only creating 1 site at a time, to limit the amount created to a manageable amount?

Thanks for any help.