Facebook already rules daily communication for more than two billion people around the world. Now it wants its own currency, too. The social network unveiled an ambitious plan Tuesday to create a new digital currency similar to Bitcoin for global use, one that could drive more e-commerce on its services and boost ads on its platforms. But the effort, which Facebook is launching with partners including PayPal, Uber, Spotify, Visa and Mastercard, could also complicate matters for the beleaguered social network. Facebook is currently under federal investigation over its privacy practices, and along with other technology giants also faces a new antitrust probe in Congress.