Facebook made big news in low-key way yesterday. It appointed COO Sheryl Sandberg to its board, making her the first woman to join the high-profile company’s highest echelon. The news was delivered by way of a 7 paragraph press release posted to the company’s newsroom blog. Given both Facebook’s profile, and Sandberg’s, the soft-pedaling struck some as odd. Part of the reason of the low-key approach may have been embarrassment, however. Facebook has been facing pressure since the run-up to its IPO from institutional investors and corporate governance watchdogs over the lack of diversity on its board, particularly over the previous complete lack of women. The news also came on the heels of the publication of “The Boy Kings: A Journey Into the Heart of the Social Network,” written by former staffer Katherine Losse, one of the earliest female hires at the company, which contains a wealth of embarrassing details about the frat-house atmosphere at Facebook HQ, including the painfully awkward way CEO Mark Zuckerberg introduced Sandberg to the staff. Still, when you’re a public company with a market cap of nearly $100 billion you don’t bury that kind of news.