TechCrunch reports that they've heard that Apple may be in late stage negotiations to buy Twitter.com for $700 million. Of course, when the site checked with other sources, they were told they knew nothing of the sort... making this rumor seem very questionable.
Twitter is a social messaging platform that allows users to broadcast short messages to "followers". The web app has seen a recent explosion in growth with massive publicity surrounding celebrity usage. Ashton Kucher and Oprah are some of the biggest celebrities to recently start participating on Twitter.
Perhaps the biggest reason to doubt this rumor is that there seems to be no clear synergy between Apple and Twitter. Twitter continues to run on venture capital funding and has yet to find a revenue stream.