It is very important that a true collaboration portal should allow the modern enterprise to collaborate directly on selected projects with clients and/or suppliers.
Extranet permissions are special in that they do not allow users to be aware of any other users in other extranet areas - in this way customer A and customer B are kept entirely separate - but with direct access to the project.
When combined with deployment through software as a service this povides an ideal solution for projects for the construction sector, where a contractor needs to collaborate with many subcontractors.