Members can constrain their interactions to the online space, or they can arrange a date to meet in person.
Opinions and usage of online dating services also differ widely.
A 2005 study of data collected by the Pew Internet & American Life Project found that individuals are more likely to use an online dating service if they use the Internet for a greater number of tasks, and less likely to use such a service if they are trusting of others.
Under this metaphor, members of a given service can both "shop" for potential relationship partners and "sell" themselves in hopes of finding a successful match.
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.
Reuters research puts that number much higher: More than 41 million of the 54 million-plus single Americans (or 76 percent) have tried online dating.