By Nin-Hai Tseng, reporter

In the world of social media, some of America’s biggest corporations are taking on more risk to build an online global brand, said Sheryl Sandberg, Facebook’s chief operating officer, at Fortune’s Most Powerful Women’s Conference Tuesday.

Communicating with the online world has been a dicey topic for many corporations. It often gives legal teams headaches over potential liabilities over how a product or company message is communicated to the public. But executives are catching on and they’re changing the way they view social networking sites – seeing it more as an avenue to build the company’s brand than being a liability.

“They’ve shifted their tone,” Sandberg said.

In a discussion during the panel, “Building a Network,” a representative from Siemens said the company has begun using Facebook to communicate internally among its diversity groups.

Also, there’s growing potential as far as using it as branding and communications tools for B2B companies. An American Express (AXP) representative said Facebook has been important for its connections with customers especially with small businesses.

Still, measuring what a Facebook friend is worth to a company isn’t easy. And it’s not always clear if the risks outweigh the benefits. But Wendy Clark, Coca-Cola’s (KO) senior vice president of integrated marketing communications and capabilities, says Facebook’s relevance is quantifiable. For instance, studies have shown that fans versus non-fans tend to spend more on Coca-Cola products, she says.