Traditional media of all stripes are struggling through their most turbulent period in a generation. Behind the upheaval and soul-searching -- the falling profits, staff cutbacks, content and programming changes, and fear for the future -- lies a stark reality: The rapid growth of online advertising is threatening the historic dominance of print and broadcasting.

Perhaps more than any other factor, the targeted advertising model perfected by Google Inc. and embraced by Yahoo Inc. and Microsoft Corp.'s MSN has curbed advertising growth at ''old media" such as newspapers, magazines, television, radio, trade publications, and direct mail.

The online challenge already has caused sea changes across the news and entertainment fields, from the rise of pay-per-view and reality television to the bidding for the financially underperforming Knight Ridder newspaper chain.

But the challenge may only be intensifying, according to a new ad spending study by Outsell Inc., an information industry research firm in Burlingame, Calif., that recently surveyed 1,200 advertisers with a combined advertising budget of $2.4 billion.

Get the full story at The Boston Globe