Billionaire Facebook cofounder Eduardo Saverin has given up his U.S. citizenship in advance of the social network’s planned initial public offering, a move that could save him on taxes. The Brazilian-born Saverin now lives in Singapore, and stands to profit handsomely from Facebook’s IPO. In other news, Facebook’s nearly $100 billion initial public offering has come under review by the Federal Trade Commission, the Financial Times reported Thursday. Neither Facebook nor the FTC would comment yesterday on the alleged investigation by regulators into the social network’s acquisition of Instagram. An FTC investigation of the deal would be routine considering the massive size of Facebook’s planned IPO, but a probe could toss a monkey wrench in plans to go public next week.