Facebook treads carefully after its vital role in Egypt's anti-Mubarak protests

In Egypt, the tried-and-true tool for opponents of President Hosni Mubarak in recent years has been Facebook. Most recently, it was on Facebook - which boasts 5 million users in Egypt, the most in the Arab world - where youthful outrage over the killing of a prominent activist spread, leading to the protests in Cairo's Tahrir Square and Mubarak's promise to step down this year.

But Facebook, which celebrates its seventh birthday Friday and has more than a half-billion users worldwide, is not eagerly embracing its role as the insurrectionists' instrument of choice. Its strategy contrasts with rivals Google and Twitter, which actively helped opposition leaders communicate after the Egyptian government shut down Internet access. The Silicon Valley giant, whether it likes it or not, has been thrust like never before into a sensitive global political moment that pits the company's need for an open Internet against concerns that autocratic regimes could limit use of the site or shut it down altogether.