A multi-site setup for this may be overkill. There are a ton of plugins for wordpress available that allow you to manage user permissions or add new features. I would recommend finding a set of plugins that meets your needs and then assigning different users to different roles or groups.

It depends. Can you describe a little more about what you will be doing?

WordPress Multisite will do just what you describe out of the box, once you get it running: users will have access only to the things you (the Super User) give them access to.

The downside to WP Multisites is that if you ever do need to branch off a particular site on its own it is not an easy task (although it is possible, I have done a few in the last month...it takes me about an hour, but I know what I am doing)

The upside to WP Multisites is the shared user database...so you can manage all users easily. It also makes updating your sites much easier, since you just have to run the updates and then it asks you to update the "Network of Sites"...you click a button and Done!

I have a few WordPress multisites running. I keep them specifically for low-traffic sites that have shared users. Works great and makes maintenance easier.

For heavier traffic sites, or sites that security is an issue (e-commerce sites) or sites that might use a lot more resources (e-commerce sites), I keep them on their own individual WordPress install...actually I keep them on their own droplet as well.

@sierracircle I run an online travel magazine where the main site/blog is managed by a team of editors. It requires a specific theme & plugin customisation that will look different from the rest of the site. There will be a different blog section where users can post their own articles.

The other sections of the site are more user-generated such as the contents in the directory and classifieds. This may not be limited to the different functions we may run such as a kickstarter or premium membership section where users can purchase content. A forum or some-sort would definitely be great for a community-driven site.

We might run an actual e-commerce site in the future but I think I'd likely take your recommendation and have it on its own individual installation. (It can still derive from the same userbase?)

In what case did you need to branch off a particular site on its own?

@ryanpq If I remained with one installation on nginx, would it still be easy to spin-off other individual WordPress installations? Or would I have to tinker around to install in subdirectories in nginx? I have considered using EasyEngine but I'm not sure how well they play with standalone installation in subdirectories.