This is just an idea, but why not use WordPress Themes & Plugins across your social platform?
The idea of social platforms is to leverage the power of the crowd. Last time I checked, WordPress had over 650 different Themes & over 3,000 Plugins. Why not leverage the work from all those developers?
What if I modified my forum software to support these Themes & Plugins?
How much time would it take to simply install a theme and turn it on to have it’s styles carry across all my components?
I think it’s a good idea to at least take a look at how Themes work in WordPress and emulate that in the social platform. I have noticed here lately how sites like Google & MySpace have recently incorporated the Theme approach.
Something to think about!