Ooh, it'll be great for bbPress and am selfishly very excited! I agree with JJJ - the more I use something myself, the more I see what I could do and the more fun doing it is. This should have good results all round.

I think there's a solid market for businesses who want their own social network in addition to Facebook, Twitter, etc but want to outsource the technical aspects or make an add-on to the site and simply use current in house community managers / pr to run it. The Audi example is perfect.

Price-wise, it's not something I could use for the site I run with a mid size forum (70k registered users, not sure how many actively post at any given time) but the advantage to starting small is working all of that out. It's definitely a surmountable problem. If it helps, at my size and with the traffic, I'd be ok paying £500 - £1000 a month, depending on how good support is, how flexible the platform etc. This is about what hosting costs me (managed WP host) with a bit extra on top because dev costs could go down. To be completely honest though, I am somewhat cheap, so take that with a grain of salt.

I'm really excited, I've been thinking about how I would do it all morning, and will love to see how this works out. Good luck with it!