Ask HN: How to convince site visitors to "Sign up with Facebook"?

Hi. I recently announced the pre-launch of Kloser.me on HN (https://news.ycombinator.com/item?id=5611680). Kloser uses authorized facebook data to connect and match people with similar interests and personalities. On the first day of launch, I was able to get 250+ visits thanks to HN, but only a few ended up actually "Signing up" for the service, using Facebook. I could have let users sign up using their emails during this pre-launch, but eventually such users will have to authorize Kloser to import facebook data in order to get started.

Which methods you think I can use to convince users to "Login with facebook"?

Thanks.