Well, not everyone believes that. Having 400 ad networks is probably too many, says Brian Mikalis, vice president of sales at Pandora. "We have saw a shift in Q1 2010, a downward trend forecast, and thought that would change in Q2, but we didn't," he says.
It appears the majority of publishers allow the buy side to dictate "a lot of stuff." Some publishers are not going there, (though I'm not quite sure where "there" is). General economic conditions have started this shift.