Twitter‘s market value increased by $11B just seconds after shares began trading on the New York Stock Exchange. The company sold its stock for $26 a share. In the first few minutes of trading they hit a high of $50.08. Assuming that there’s no sharp change, Twitter should escape the criticism that hit Facebook when it went public 18 months ago — that the company had been too greedy and charged too much. Its share price fell shortly after the IPO, and didn’t return to the opening price until the middle of 2013. Pivotal Research Group’s Brian Wieser said this week that he expected the stock price to rise rapidly after the IPO. He added, though, that it “will¬†inevitably face some downward pressure at some point, whether because of sales due to lock-up expirations (which should occur in both February and May of next year), because of short-term mis-steps by the company (perceived or actual), competitive actions by¬†competitors or because user trends fail to meet investor expectations.”