I would assume that most of the money would come from the sites in the banner adds as there is no way businesses like kik or skype would want their names associated with sites like this. you ever wonder how sites like facebook, myspace, tumblr, youtube etc. managed to make it big without ever charging users a dime? its a combination of being paid to have adds on site and doing advertisements for themselves offsite.
the only reason the free model isn't working is because there is no advertisement for this site so there is not enough foot traffic leading into the site.
also, I have investigated plenty of required fee sites, they still have bots and scammers, many of which are endorsed by those sites themselves as a way to get more money and to make users feel like the site is more active than it is.