The microblogging site Twitter turned down a 500 million dollar purchase offer from the social networking site Facebook in 2008, according to the Financial Times. In an interview with the British business daily published over the weekend, co-founder Biz Stone said Twitter wanted to become not just a popular site but a viable business, rather than be taken over by another company. "We've created something that people are finding value in," he said. "But we haven't yet created a business out of this, and we really wanted to do that." According to the Financial Times, Facebook CEO and co-founder Mark Zuckerberg offered 500 million dollars in Facebook stock for Twitter. But Stone said Facebook had nothing that Twitter's three co-founders -- Stone, Evan Williams and Jack Dorsey -- wanted. The daily added, without elaboration, that Twitter still isn't turning a profit more than four years after it was created. In mid-December, Twitter said it...