About reporting scammers:
you should report scammers on the paid sites, like match.com, as they might be paying with somebody's stolen credit card, and their accounts should be removed asap, to avoid recurring charge of a victim's credit card. It is harder for them to get back on such sites as a paid members, as they not only have to register, but also obtain another stolen credit card number somewhere.
As for free dating sites or social networks, there is not much point in reporting. 99,9% of sites don't care about scammers. They are making money from traffic (advertising) - more traffic the better, doesn't matter if it's a scam traffic or real people, advertisers pay them the same for both. Reporting them to such sites actually does harm to our scamfighting cause, because they will re-register right back, but with a brand new name, e-mail and picture, and all efforts in exposing them will become vain. Better if they stay on the site with old info, so victims can find this info here through google, and realize they are being scammed.