I like the badges idea. Airbnb works that way. When accepting guests, it's helpful to know that they have attached their facebook, email and/or phone number because once they do that they can't set up a second account attached to those accounts or numbers. That means it's not as easy to run away from a badly reviewed account and just start fresh. Reputation is important.

I still think website perks and privileges based on SP would be a great way to determine which accounts are truly invested and that incentivises people to invest too.