It wasn't that long ago that LinkedIn seemed destined to be a perennial social third wheel behind Facebook and Twitter. And while Twitter has enjoyed explosive growth in 2012, Facebook has, for the most part, taken a beating. Its stock price has dropped 47% since its May IPO, as it struggles to accelerate sales growth and mobile advertising, and there's n ews spreading that 83 million of its users may come from dubious sources such as duplicate accounts and spam bots. LinkedIn, in spite of a data breach, has flourished in 2012. Its revamped home page has resulted in record levels of activity, LinkedIn said at a town hall event on Aug. 2, and its stock has risen 48% so far this year. Sales nearly doubled in Q2 2012 compared to a year ago, according to CNNMoney. But what's important for the investor may be only indirectly important for the PR pro. It's safe to say that LinkedIn's value as communications platform continues to grow.