ranking social content created and shared and filtering out the noise is I think the biggest problem with current gen of social networks and though fb's edgerank is better than anything else out there I still find myself on g+ to avoid the overload. but the biggest offender is twitter using only time as the decision making point to update me about my interest graph is not very effective (and its slow loading of old tweets doesnt help either). [though if its only intended as a real time feed I may be using it wrong]