A deal of this magnitude will have implications far beyond Omnicom and IPG. Agency heads tell us what they think of the motives – and what it means for them.

Omnicom shook up the advertising world Monday by announcing its plan to buy rival Interpublic Group of Cos. in a deal that would create the world’s largest agency holding company .

Omnicom Group says agency leaders will remain focused on clients during the acquisition and integration of Interpublic Group.