From the set to the 'Net: online advertising was Topic A at the UBS conference.(AD...

Some of the ad industry's top executives recently offered rare public glimpses into how America's shift toward digital media is affecting Madison Avenue. Their view: Agencies are being radically transformed by the changes in the media marketplace, especially the explosion of online searches and broadband video.

"The big shift has been in Internet usage," said Martin Sorrell, chairman/ CEO of London-based WPP Group, the largest buyer of media time and space in the world, during a presentation at UBS' Media Week conference in New York last week. Sorrell, whose units incl