Pop stars command the five largest followings on Twitter, so a pop-heavy list of trends should be no surprise this week -- or any week.

Facebook Inc. gained as much as 18% in its trading debut, following a record initial public offering that made it more costly than almost every company in the Standard & Poor's 500 Index.

Plans for a third agency network at Mediabrands are finally firming up. The new unit will sit under the Orion Trading Unit and handle conflict business.

USA actors posted messages to Twitter while onstage at the network's upfront presentation while fans tweeted outside.