I think you need to dig down further on the customer question. Are your users going to be say small community clubs with 20 members using it for chatter, or fan

I think you need to dig down further on the customer question. Are your users going to be say small community clubs with 20 members using it for chatter, or fan boards with hundreds of thousands of users, or companies using it internally. What does the ROI look like from the user perspective, are your users going to recoup costs through sell subscriptions to member only forums, run advertising, or are they going to be funded via patronage ?