In countries and cultures in which arranged marriages are common, sites such as India's Shaadi and Bharat Matrimony, which boast many millions of clients, are a big hit with young people who want to influence how their marriage partners are chosen.
And a number of sizeable digital matchmakers, including Jiayuan and Zhenai, have risen to prominence in China.
Deepak Kamra of Canaan Partners, an American venture-capital firm that has backed several dating services, including Zoosk and Bharat Matrimony, estimates that the industry's revenues from membership fees and advertising now amount to billion-4 billion a year.
Some, such as JDate, which is designed for Jewish lonely hearts, and Ave Maria Singles, which focuses on Catholics, serve specific religious or ethnic niches.
Others appeal to rather less conventional interests.
Vampire lovers can sink their teeth into the profiles on offer at Vampire Passions, while those obsessed with i Pads and i Phones can hunt for their i Beloveds at Cupidtino, a dating site for fans of Apple's products.
FOR the lovelorn, the new year can be an unhappy time, as they cast envious glances in the direction of lovey-dovey couples at the season's parties.
For online-dating agencies, it is a golden opportunity, as people who have spent the holidays ruminating over unsatisfactory or non-existent love lives log on in their thousands, hoping to find romance—ideally before February 14th.
“The period between New Year's Day and Valentine's Day is our busiest six weeks of the year,” explains Sam Yagan, the boss of Ok Cupid, a big American dating site.
Once seen as the last resort for a bunch of lonely geeks, online-dating services have gradually shed much of the stigma formerly associated with them.
Although they are still popular with tech types—Julian Assange, the mercurial co-founder of Wiki Leaks, reportedly once maintained profiles on dating sites under the name “Harry Harrison”—they now attract millions of people from many walks of life.
Com Score, a research firm, says Match and Zoosk, two large dating services based in the United States, saw 4.6m and 4.8m unique visitors respectively come to their American sites in November 2010.
Meetic, Europe's biggest dating service, also boasts millions of users.
Blowing cyberkisses has become a popular pastime in emerging markets too.