Google is in negotiations to acquire Twitter, according to a report on TechCrunch – although its sources disagree on whether the negotiations are in their early or late stages. The story suggests that the deal would value Twitter at “well, well north” of its existing $250 million valuation.Why buy? The value of Twitter is increasingly as a live search engine – as millions more people use it, the value of digging into what they’re tweeting about in real-time is potentially huge to someone like Google. It’s no surprise that Twitter has been working hard on making its search more closely integrated into the site, as co-founder Biz Stone explains in a blog post.Twitter rebuffed an acquisition offer by Facebook earlier this year – if a deal with Google goes through, we’ll know why.