Ever-diminishing buying points

The announcement today (FT) of the creation of a new media-buying network controlling $4.2 billion of combined ad buying means that media-buying decisions are about to concentrate in even fewer hands. How many people are now actually making the top-line strategic decisions as to where the ad money should be going? WPP, Aegis, Publicis, and now Columbus Media International (MediaWeek). I've said before that old media - especially TV, print - is unduly optimistic if it hopes that revenues will continue to merely decline at a predictable and gradual rate of a few percentage points a year. There are so few advertising buying points - people making the real strategic decisions - that there's no reason for a manageable decline to continue to be the case. The risk for the media owners is located in a vanishingly tiny number of hands and this becomes (fairly unusually, given how widely and indiscriminately the term is used) a tipping point situation. Say for the sake of argument that four people, or at most four steering committees - one each at WPP, Aegis, Publicis and now Columbus - say "screw TV, it's relatively overpriced, the mass audience just isn't there any more and we'd get a better ROI online". Is that goodnight for TV's commercial model?