At this time, you would need 10 LiveIDs and each subscription would handle 3 computers. A hub is a member of the Circle, so that means 10 hubs. One hub cannot manage multiple subscriptions.
The limitation is a license is for up to 3 computers = a subscription and one LiveID can have only single subscription active for it.
This may change in the future, but nothing has been announced. You may be interested in a product due later this year which, from the press release, sounds like it might fit the bill for a small business environment. It is the next version of Small Business Server that will include a version of OneCare that can manage the client PCs in the environment. More than that, I don't know at this point.
-steve