Thanks for your feedback!
Great point about the most efficient way to meet a partner! This is indeed a great question one should ask oneself. I see a problem with that approach though: I guess many people don't want to mix 'efficiency' with dating and human interactions and emotions too much. It's probably socially accepted to use dating sites, but are we already on our way to rethink our entire approach to dating?
The expression of interest is indeed a good concept to hang on to. Which is why social networks are especially suitable for adding dating - you can add a simple "are you open to dating approaches?"-setting.