Fenwick & West corporate partner Ted Wang has a simple explanation for why his firm decided to join the "Lean In" campaign launched earlier this month by Facebook chief operating officer Sheryl Sandberg in conjunction with the publication of her buzzed-about new book of the same name that aims to help women advance in the workplace.

"If Sheryl’s involved, it’s a good thing," he says.

Wang should know; Silicon Valley–based Fenwick is the firm that helped take Facebook public in 2012. He insists, however, that the involvement of a top executive at one of Fenwick’s key clients was not the only draw. "We have a problem, and we think this will help us," he says, pointing to the fact that women represent half of Fenwick’s incoming associate class, but only 17 percent of its partners and just one in 10 members of its executive committee.

Fenwick is one of five Am Law 200 firms among the more than 150 companies and organizations that have signed on as partners to Lean In, which encourages women to take control of their professional careers, in part by openly discussing the challenges they face both at home and at work. The other firms lending their names and support to the cause are Orrick, Herrington & Sutcliffe; Sidley Austin; Skadden, Arps, Slate, Meagher & Flom; and Weil, Gotshal & Manges.

As Sandberg, 43, explains in a video on the Lean In website, the campaign is based on the idea that to make real progress professionally, women need to talk with each other, as well as their male counterparts, to change the fact that "We don’t sit at the table, we don’t raise our hands, we don’t let our voices be loud enough." Sandberg, who joined Facebook in 2008 from a position as vice president of global online sales and operations at Google, pushed the same message in a powerful 2010 speech delivered at a TEDWomen conference on why the business and political world has too few female leaders.

Although the Lean In movement does not specifically target the legal industry, there is ample evidence that large law firms are marked by significant gender inequality. Even though women have been entering law firms in almost equal numbers to men for years, they now make up, on average, just 15 percent of the equity partnership ranks at the nation’s 200 largest law firms, according to a report issued in October 2012 by the National Association of Women Lawyers.