I've come to the decision to charge $5/year for a site I'm going to put online in the next year... only to cover the transaction fees and mostly actual costs. If it takes off, should at least pay for itself and discourage fake accounts. But not every site/service will get that many people to even pay that much.

On the latter bit... not sure if I completely disagree with that take as well. As much as I also dislike SSO for other reasons, it is nice as at least some level of validation.