Salesforce.com announced today that it would make its Force.com platform available to build applications for Facebook, in a move that's sure to ripple through the social networking space. Facebook rival LinkedIn, the business social network for professionals, just launched its social networking applications platform last week.

The announcement was made jointly by Marc Benioff, Salesforce.com's CEO, and Sheryl Sandberg, COO of Facebook, at the Dreamforce conference in San Francisco.

"Businesses are reaching consumers on Facebook," says Facebook's Sandberg. "One of the most common questions we hear [from those businesses] is how do we use Facebook more? We have a page there, and it's going well, but how do I use the power of Facebook to really engage in a deeper way with these constituents?"

She continued, "By coming together with Force.com, we believe we can open up productivity and enterprise apps for our users," she says.

Developers using the Force.com platform can create an enterprise application there, then run it through what Sanberg called the Toolkit for Facebook, which allows the same application to work on Facebook.

The Force.com application will appear embedded in Facebook, but (and this might be to the delight of enterprise IT managers) it is hosted on Salesforce.com's Force platform, which is regarded as enterprise-worthy while Facebook's infrastructure is looked upon as consumer-grade.

As an example, Salesforce.com executives and Sandberg showed off how a recruiting app made on the Force.com platform could be embedded into a Facebook page. The app leveraged the social aspects of Facebook to determine what "friends" on the service might be a leading candidate for a job listing.

Such an example shows how business-focused applications can utilize Facebook's "social graph," what Sandberg and the company's CEO, Mark Zuckerberg, (in his public appearances) refer to as showing the connections between friends, family and colleagues.

Facebook, which has nearly 28,000 applications on its platform, has not generally been focused on the enterprise or productivity. As Sandberg noted during her part of the keynote, Facebook apps have centered around games, sports, music, and advocacy.

"We think there is a need for more productivity and enterprise apps," Sandberg says. "You can build it on force.com and run it on our platform. We think this partnership is a really exciting step."

Last week, LinkedIn, the social network for professionals, launched a very focused application platform that brought nine applications to users. Analysts called it a departure from the playful, game-like applications of Facebook.

This announcement could turn the LinkedIn news on its head, seeing as the enterprise apps developed on Force.com are very business-focused and allow for customized company processes.

"It's bringing the two platforms together," Benioff says. "It changes what you can do on Facebook's social graph. You can create social applications, such as social CRM."