In Germany government financed NGOs like "Verbraucherschutzzentrale" sometimes help to sue online dating sites.
Some sites provide free registration, but may offer services which require a monthly fee.
Other sites depend on advertising for their revenue.
The highest scoring dating service was Facebook, which uses the personal homepage genre, the message board genre, the weblog and directory genre, as well as utilizing the Circle of Friends.
The second highest scoring, Second Life utilizes virtual worlds, message boards, chat groups and profile pages to allow people to contact in a three-dimensional environment.
Since 2003, several free dating sites, operating on ad based-revenue rather than monthly subscriptions, have appeared and become increasingly popular.