Of course, there are also question marks about advertising on social networks, primarily because their content is mostly unregulated, and sometimes objectionable, as it is generated by millions of individuals. In addition, social networking sites are under close watch by law enforcement agencies worldwide, because sexual predators have used these sites to stalk and victimize others, including minors.

An earlier sign of Google's sense of urgency about the social networking market was its reported courting of Facebook when the latter was recently seeking a partner to invest in the company and earn a deal to provide advertising to it.

Microsoft eventually won, buying a 1.6 percent stake that values Facebook at an eye-popping US$15 billion, although the social networking company reportedly will have revenue of just $150 million this year.

With about 300 employees, Facebook expects to have about 700 a year from now, its CEO and co-founder Mark Zuckerberg recently said. About 250,000 new users register every day at Facebook, which was founded in 2004.

In June, MySpace, owned by News Corp., had 114.1 million unique visitors worldwide, ranking first among social networking sites, followed by Facebook with 52.2 million, according to comScore. Hi5 ranked third with 28.2 million, while Friendster was fourth with 24.7 million. Orkut rounded out the top 5 with 24.1 million.

OpenSocial, which will launch officially Thursday evening, represents "the first release of technical details" for the forthcoming MySpace application development platform, Google and MySpace said on Thursday.

MySpace and Google, which have an existing relationship in which MySpace runs ads from Google's ad network, have been in talks for the past year about possible collaborations in the area of social applications, MySpace said in a statement.

MySpace's own application development platform will launch "in a few months," but with the OpenSocial APIs, developers will be able to start writing applications for MySpace immediately.

"The applications will be able to be tested within the MySpace environment and then the MySpace Platform will officially go live in the coming months," the MySpace statement reads.

MySpace's platform will allow third party developers to develop widgets that "deeply integrate into MySpace features" and network.

Some applications built with the OpenSocial APIs will be available in test mode on the MySpace site prior to the platform's launch.