This is brilliant on two counts:

1. There is a well known adage that goes something like, 'if the service is free, you're the product.' One could easily think the inverse is true ('if you're paying for the product, you're the customer') but obviously in the light of this case it isn't necessarily so. But making users pay for the service likely decreased their level of suspicion.

2. Need to tie a pseudonym to real person? A credit card number, bank account, or even a bitcoin public key get you a long way toward that goal.