Multiply is an innovative social network that allows you not to shahe only your images, but to share all you've got.

* post digital photos, videos and music * publish your own blog * schedule events and parties on your social calendar * share movie or restaurant reviews

Standard feature is comments : Others can comment on whatever you post (share) on Multiply, making it a discussion board as well. This certainly looks promising.
Multiply is not alone : Techcrunch recently reviewed Filemobile.