I recently answered a post in the MSDN Forums asking about best practices for organizing team projects (Organization of Team Projects). For my own benefit, I’m going to post it (and update it) here so I can find it more easily.
We've asked our patterns & practices team to develop content that addresses Team System best practices, but that will take some time to create as they need to evaluate many practices before they can promote one or more as best practices. In the interim, here are some things to consider, which shouldn't be misconstrued as representing official guidance.
Of course, you can only consider something to be a best practice within a given context. Below are some context variables that could sway a decision one way, or another.
That said, we built Team System using a single team project with a large development team dispersed around the world. Was that the best choice? Maybe, maybe not.