Very interesting comparison of Social Activities Services

MINGER.NET has a very interesting look at some of the major Social Activities Services available today. I particularly like the diagram depicting some central dimensions to consider when choosing a service to use. Personally I would further like to see these services pick up on the functionality that sites like meet-o-matic, MeetWithApproval.com and agreeAdate deliver, namely a simple and powerful mechanism to negotiate a date for a future event.