While some sites conduct background checks on members, many do not, resulting in some uncertainty around members' identities.
For instance, some profiles may not represent real humans but rather "bait profiles" placed online by site owners to attract new paying members, or "spam profiles" created by advertisers to market services and products.
Still others rely solely on paid membership subscriptions.
Opinions and usage of online dating services also differ widely.
Most free dating websites depend on advertising revenue, using tools such as Google Ad Sense and affiliate marketing.
Since advertising revenues are modest compared to membership fees, this model requires a large number of page views to achieve profitability.
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.
Online dating services allow users to become "members" by creating a profile and uploading personal information including (but not limited to) age, gender, sexual orientation, location, and appearance.
Other sites target highly specific demographics based on features like shared interests, location, religion, or relationship type.
Online dating services also differ widely in their revenue streams.
However, Sam Yagan describes dating sites as ideal advertising platforms because of the wealth of demographic data made available by users.
There are mixed opinions regarding the safety of online dating.