WOuld my site benefit from Multisite?

I run, manage, and designed ArgueThat.com
The current-live version is not my final product by any means, I'm soon launching a new platform entirely.
This new platform, as of now, will include a Buddypress installation on top of WP 3.4.2.
I'm wondering if It would benefit from a Multisite installation (that is my question). I don't necessarily want my users to have their own blogs, just post to the same blog with various categories. But it's still a social network in that I want them to be able to privately message each other, send friend requests, and receive notifications of these and of new comments on their posts.

Any advice would be greatly appreciated.