It's not just Kleiner Perkins under fire. Last week Twitter and Facebook were sued by former employees for alleged gender discrimination.  A former Twitter engineer, Tina Huang, filed a proposed class action lawsuit against the company, alleging it uses secretive promotion and hiring processes that favor men. Twitter responding saying: "Ms. Huang resigned voluntarily from Twitter, after our leadership tried to persuade her to stay. She was not fired. Twitter is deeply committed to a diverse and supportive workplace and we believe the facts will show Ms. Huang was treated fairly."  The law firm representing Pao, Lawless & Lawless, is also suing Facebook on behalf of a former employee, alleging that she faced discrimination, harassment and retaliation because she's a woman and of Taiwanese descent. Facebook said in response: "We work extremely hard on issues related to diversity, gender and equality, and we believe we've made progress. In this case we have substantive disagreements on the facts, and we believe the record shows the employee was treated fairly."  Facebook COO Sheryl Sandberg has been an advocate for Facebook and all of corporate America to embrace gender equality with her "Lean In" movement. And she's said that Facebook can and should do better. Last June, Facebook reported that 69 percent of its overall global work force is male. That's right in line with Google, Apple and Twitter, which all reported a 70 percent male work force last year. Yahoo reported that its work force is 62 percent male.  Read More Silicon Valley bias suit spurs closer look by firms  There are even fewer women in the executive ranks. At Facebook women comprise just 23 percent of senior ranks, but that's far better than the average. At Silicon Valley's top 150 companies women comprise just 11 percent of executives, compared with 16 percent at S&P 500 companies, according to a report by law firm Fenwick & West.  These statistics of gender inequality at top Silicon Valley companies have wide-reaching implications. These corporate giants are a key training ground for entrepreneurs as well as VC investors. So improving the balance at the biggest companies is key to drive equality across the tech and start-up ecosystem.
Industry insiders and attorneys are mixed on whether Ellen Pao's lawsuit will have a chilling effect on hiring women in Silicon Valley.