The dating space is interesting. I think it's ripe for disruption. But thus far I haven't been able to figure out how to attack it, let alone where to start.

I think YC was right when it said you have to concentrate on solving the chicken-and-egg problem.

"...anyone who wants to start a dating startup has to answer two questions: in addition to the usual question about how you're going to approach dating differently, you have to answer the even more important question of how to overcome the huge chicken and egg problem every dating site faces. A site like Reddit is interesting when there are only 20 users. But no one wants to use a dating site with only 20 users—which of course becomes a self-perpetuating problem. So if you want to do a dating startup, don't focus on the novel take on dating that you're going to offer. That's the easy half. Focus on novel ways to get around the chicken and egg problem."

If you're passionate about building an online dating site, I'd spend all of my time iterating ways to get users. Try a bunch of different ideas. And fail fast.

#8 http://ycombinator.com/ideas.html