Just to give you one user's perspective (which honestly, by virtue of being a HN reader probably represents a very small fraction of general users); anytime I see a service that requests I login via FB or Google, I assume you're trying to mine my personal data. Unless you are Facebook, or Google, or maybe LinkedIn (with whom I'm already willing to share my personal data) I'm not going to use these options. Make this your only option and I'm going to close the tab.

No personal offense to you, or your business. Just telling you as a geek, this is a non-starter for me.

But they are trying to mine your personal data, to confirm that you're real, and to get to know you better so that they can match you. It's really all up there on their website.

Your comment is perfectly in line with my second paragraph.

I got sloppy with wording in my third paragraph, but meant the same thing again. (We want a better dating site. We think that FB is a good tool to use for that. Etc.)