For viewers, it probably goes fairly unnoticed (consciously). But for candidates in televised debates, the split screen is a pain in the ass.
From the New York Times:
The split-screen effect has become such a modern media phenomenon that political scientists have studied it. In one study conducted by University of Wisconsin researchers, 700 college students were shown five-minute segments of the Sept. 30, 2004, presidential debate between Mr. Bush and Mr. Kerry. One clip was a split-screen, while another was a single screen.
The study concluded that watching a debate on a split-screen considerably reinforces negative perceptions that people have about the candidate they oppose. If a candidate is signaling displeasure with his opponent’s response by sighing, for example, that creates an even more negative perception of the opponent among the candidate’s supporters.
The Times notes that President Obama suffered in last week's debate at the hand of the split screen. He was often seen avoiding eye contact with Mitt Romney. Even liberal comedian and commentator Bill Maher said Obama came off as "rude."
But while the major networks and cable news channels plan on utilizing the split screen in each of the debates, there is one reprieve: PBS doesn't.