I see several flaws with people who aren't on Facebook, all of which are dating dealbreakers.
1. You are antisocial. – This will cause all sorts of problems in your relationship from the mild never wanting to go out to major things like isolation from your friends and family. The antisocial person may also be very jealous of time you want to spend out and about with other people.
2. You don't have friends. – See #1
3. You have something to hide. – I'm pretty sure that serial killers don't have Facebook profiles. If you meet someone who can't even put up a simple, basic profile, this is suspect. In fact, many companies reject resumes from people that don't have Facebook profiles now. If you can't get a job without a profile, you shouldn't get a date either.
4. You don't have a computer or other device that will connect with Facebook. – In this day and age, if you don't have access to technology, even at the public library, there is a serious issue. Nun's tweet, have cell phones, and blog. Homeless people have laptops. I find a complete lack of technology utterly suspicious.
5. You don't have time. – If you don't have time for Facebook, chances are, you don't have time for dating.
I'm not saying you need to be on Facebook all the time in order to be datable. You do need to at least have a profile and some friends. Real friends, not just bands and movies. I highly recommend filling out a little info about yourself as well. Is your personal security really threatened if you tell people the last book you read? It may save you a lot of hassle. Some books make people undatable.
You can ditch all those books about how to date and just follow this theory. It works every time.