Such sites earn revenue from a mix of advertising and sale of additional options.
At the end of November 2004, there were 844 lifestyle and dating sites, a 38% increase since the start of the year, according to Hitwise Inc.
The stigma associated with online dating dropped over the years and people view online dating more positively.
Over 50% of research participants in a 2011 study did not view online dating as a dangerous activity, whereas 43% thought that online dating involved risk.
Because online dating takes place in virtual space, it is possible for profile information to be misrepresented or falsified.
While some sites conduct background checks on members, many do not, resulting in some uncertainty around members' identities.