Can the Multi-Domains plugin be monetized via Pro Sites like the Domain Mapping plugin?
i.e. Give users two paid options:
1) Buy their own domain or
2) For a lesser fee offer sub-domains on premium domains already owned by the site while still allowing free blogs on the main domain(s).
If it can't already do this, it would help generate more revenue from less important or temporary blogs where the user doesn't want to go through the hassle of setting up a unique domain but would like a more "topic friendly" URL than the site's domain name. For example, Edublogs.org could have a series of course subject related domains like blogname.physicsinstruction.org, blogname.dramastudent.org, etc.