In May, LinkedIn went public. To much fanfare, the business-oriented social networking site sold common shares at $45 each, for a total offering of $352.8 million and an overall valuation — public and private shares — of $4.3 billion. It was the biggest Internet initial public offering since Google went public in 2004. At one point on opening day, a share was trading at over $94, bringing back wistful memories of the dotcom boom of the late 1990s. At the end of the day, the company was worth $8.9 billion.