Some ROI results for those on Twitter. From The Wall Street Journal: "Dell sells $3 million through Twitter,"
We’ve surpassed $2 million in revenue in terms of Dell Outlet sales, but we’re also seeing that it’s driving interest in new product as well,” wrote Stefanie Nelson, one of Dell’s Twitter administrators.

Customers arrive at Dell’s online outlet store through the @DellOutlet Twitter account, but many wind up buying new Dell PCs, pushing overall sales over $3 million.