This is my current startup attempt: http://forwardingtree.com. Also see: http://groups.google.com/group/forwarding-tree. Note that personalization is just another way to control spam. One might imagine an extension of the social network approach used that would apply to discussion forums for example, even at the level of individual threads/posters. How would you personalize a discussion and yet still retain something that is coherent?

I'll present some other ideas here soon.