Overall, I think Yoomoot is a great concept and is doing a good job of organising what would otherwise be a great number of messy discussions. The question & answer format at first is an odd concept to get one's head around, but it does work.
However, because moots are restricted to this format and the only other type of moots presently are bookmarks or articles the social interaction between users is nothing more than a conversation of just questions and answers. A real conversation and deeper social interaction goes far beyond just asking a question and getting an answer (although I accept it is a massive part). Social interactions - especially on web 2.0 and beyond sites - go beyond text and allow the exhange of videos, images, sounds and are less restrictive on how that is shared. A video posted online for someone to see / interact with doesn't have to be a bookmark, article or question. It can have no particular purpose other than simply to engage a friend or make contact.
My point is that at the moment, whilst I am enjoying contributing and getting involved in discussions, my level of social interaction with individual users is still at arms length and I don't feel like I have developed any particular bonds/networks with one person or a group of people. I acknowledge though that in these early days, I shouldn't expect to and these things take time.
I hope I am proved wrong :)