My dad met his wife on Match.com and he's happier than he's ever been and from what I can tell, far more in love than he ever was with my mother who he (obviously) didn't meet online considering they met in the 80s.
I doubt it's any different than meeting in person. In person you do the same things, determine if you're physically attracted then start talking to them to see if there's any type of connection/other attraction. I don't see how it's any different online. I doubt my dad was matched with his wife and thought "well she answered the basic questions well, we should be in a relationship". I'm sure people looking for something beyond sex talk and date for a while before thinking someone is relationship material.
I just think the free ones attract the crazies aka my friend and her fiance.