To me, the value proposition on forums (and newsgroups, their spiritual fathers) is very strong.
Facebook: why am I here? What is the relationship to these other 250 people on my friends list?
With forums, there's a joining thread of shared understanding.
The guys at one forum know who I'm talking about if I name-drop Commodore Smoker.
The guys here don't, but they can tell a M10 from a M1 from a M.
I'm not sure putting on an image-uploader or an oekaki-style feature adds much to that type of relationship.