Fotolog Inc., one of the leading user-generated photography blogs and social networks, has launched a mobile service as part of its plan to add new features and revenue streams for continued growth.

The expansion comes as Internet publisher Hi-Media Group claims that Fotolog has surpassed the 20-million-member mark and is now the world's largest photo-blogging Web site and the fourth-most-active social network. The Fotolog mobile service is accessible via Web-enabled phones at http://m.fotolog.com.

"Our mobile strategy is an outgrowth of Fotolog's business model and also reflects the unique business strategy of our parent company, Hi-Media Group," said Andrew Cohen, general manager of Fotolog, New York.

"We've grown explosively since we were founded in 2003 due to the high level of participation and engagement of our global photo-blogging community," he said.

Since the site's acquisition by Hi-Media was announced last year, Fotolog's rapidly growing community has created one of the largest global inventories of user-generated content, with more than 600 million photos.

Fotolog has grown virally via word-of-mouth promotion since its founding, with virtually no marketing or member incentives.

However, Fotolog has entered into a series of 25 select cross-promotional relationships with various online media partners serving key U.S. audiences.

Fotolog expects to start hosting mobile advertising campaigns in the near future.

"Based on our experience so far, our mobile site is of interest to major brand advertisers looking to reach a youthful and hip audience," Mr. Cohen said. "We haven't announced any partnerships yet but will be doing so shortly."

Fotolog built up a 10-million-member community in its first five years of existence.

In the past year the company has seen a sharply accelerated growth rate, going from 10 million to 20 million members. Unique visitors in the U.S. doubled this year.

Fotolog is generating more than 1 billion weekly page views, according to the company.

The social network has also experienced key market growth worldwide. The site is now the No. 2 social network in Spain.

The model for the Fotolog user experience is counterintuitive because the site limits uploads to one per day, with the exception of premium Gold Camera subscription members. This makes it closer to a daily photo blog than a photo-sharing site like Flickr.

Hi-Media Group has applied its advertising and micro-payments capabilities, which serve more than 200,000 partner Web sites, to grow Fotolog's revenues.

For example, Fotolog recently rolled out Hi-Media's Allopass mobile micro-payments system to members in Latin America, where Fotolog has more than 12 million unique monthly visitors who generate more than 2.8 billion page views.

By enabling subscription membership payments by SMS, the introduction of Allopass added hundreds of thousands of new members across the region and created promising new revenue streams.

"We've found that by deploying SMS payment solutions we are able to market to 80 or even 90 percent of many markets, far beyond the reach of those who offer only credit card options," Mr. Cohen said.

Consumers dial a local number for Allopass to receive by SMS a numeric code. They punch the code in on the Fotolog mobile Web site to buy a subscription or a premium offering.

Allopass currently accounts for almost 3 million SMS transactions per month -- more than 1 per second.

"This simple solution is proving itself to be a powerful driver of revenue and membership," Mr. Cohen said. "Clearly, mobile applications are a critically important source of online revenues."

Fotolog this month announced a complete technology upgrade to the world's highest-volume deployment of MySQL on Solaris and a doubling of Fotolog.com's software engineering team to accommodate the site's growth.

Fotolog was acquired in 2007 by Hi-Media Group, one of the top 100 media companies worldwide, with advertising, publishing and micro-payments businesses.

"With a massive audience engaged in this way, our model demanded that we embrace ubiquity," Mr. Cohen said. "The wind at our back has been the increasing ubiquity of cell phone cameras and we had to have a mobile strategy because it's at the heart of our member experience.

"From a business perspective, our mobile capability provides revenue diversification and an important platform for future growth, particularly internationally, where we are far ahead of others," he said.