The Financial Industry Regulatory Authority (FINRA) has fined Goldman Sachs Group Inc (NYSE:GS) $800,000 for failing to prevent trade-throughs on 395,000 trades from its SIGMA-X dark pool between July 29, 2011 and August 9, 2011. Goldman Sachs also returned $1.67 million to investors whose trades were affected during that period. Market data latency caused the trade-throughs: FINRA “It is imperative that firms take steps to ensure compliance with the SEC’s trade-through rule so that displayed trading interest is appropriately protected and customers do not receive executions at inferior prices,” said Thomas Gira, Executive Vice President, FINRA Market Regulation. “In…