Comcast plans to buy Time Warner Cable for about $45.2 billion in stock in a deal that would combine the top two cable TV companies. "This transaction will create a leading technology and innovation company, differentiated by its ability to deliver ground-breaking products on a superior network while leveraging a national platform to create operating efficiencies and economies of scale," the companies said in a release.

The combined company would have 30 million subscribers - just under 30 percent of the U.S. pay television video market. The closest video competitor, DirecTV, has about 20 million video customers.

However, consumer watchdog groups have come out in opposition to such a deal.