Some people I know who refuse to date people online say so for one simple reason: "I don't know if people are who they say they are."
This is a funny comment first off because even if you met people out somewhere, at work, etc., you rarely don't know who they are until you REALLY know them. Even then, it's debatable how well you know them, not just their physical appearances, but their personalities as well.
For those of you brave enough to test online personals, TrueDater.com is a site to review and write testimonials about your dating experiences. If you've met people on Match.com, American Singles or JDate, go here and tell whether or not the person is a TrueDater. Furthermore, if you want to find out about a possible future date, this is the place to do it.
Then again, people could, theoretically, sign up and say they are great dates, and that you should go out with them. The other thing you'll need to do so people browsing the site actually believe you is have friends post on your behalf. I guess you could make up that information, too, but if you really have that much time on your hands, maybe you shouldn't be dating at all.