Here are a few of the major M&As that have occurred or been attempted within the past year, including AT&T and T-Mobile, Exelon and Constellation Energy, and Comcast and NBC Universal.
AT&T announced March 21 that it planned to buy its wireless rival T-Mobile USA from Deutsche Telekom for $39 billion in cash and stock. The deal would have created the nation's largest wireless carrier. However, the companies dropped their application in November after the FCC said it was moving to block the deal. On Dec. 19, AT&T announced that it was dropping its bid to acquire T-Mobile.Spencer Platt/Getty Images