We do not discuss what checks we do for security purposes. I can tell you this background checks are NOT the answer they are a small piece. The problem with background checks is that as soon as you say "everyone has had a background check on the site" the people let there guard down and often take the attitude of "well this person must be safe as they had a background check." Generally the best you can do with is determine is someone is a sex offender or a felon. ButI can tell you there are far more cases people are removed from social netowrking sites do to some kind of bad behvior on or offlife and they had no criminal history at all. A person can be a creep or a con-artist and not be a criminal. That is way common sense, prudence and some online googling is your best course of action when meeting ANYONE new be it at a gym, club, party, mass or online dating site.
Since the question was answered and this thread has gone off topic I am shutting this one down.