Permissions advice. Would you recommend using new confluence spaces per project (is this the intended use?) or is this unnecessary? >30 software dev projects

[TomC]

Quentin's answer is not incorrect, but I think it is fair to say that 'there is no hard and fast rule' here. It depends on a few things that are also considerations:

Here are a couple:

1) Permissions - do you prefer managing and setting up permissions for 30 different spaces or just one. Your answer will depend on numerous factors, but it's one item to consider. 

2.) Complexity - will your project likely have numerous pages or just be one or a few pages. Confluence will support either scenario, but the less complex, the more you might lean towards one space. 

Or maybe there are different ways to slice it, such as if you have numerous dev teams, would your org prefer they all 'live' in one space (and just manage page restrictions when necessary) or would they like each team to have their own space. A higher level group of manager or managers can have view access to all, but maybe the individual dev teams prefer their own secure space, where they can set up their home page as they like it, etc.

[QuentinB]

Yes, a space for a project is a good way to share information inside a team.
I think this Atlassian blog post may interest you: http://blogs.atlassian.com/2014/07/create-confluence-space-team-project-part-1-2/