Why, oh why, are the Big 4 broadcast networks doing so poorly this fall? This question is being bandied about everywhere, including this very publication. Is it DVRs? Is it Netflix and Hulu? Is it programming competition from cable? Is it Wii? Is it YouTube? Is it live plus 3 days ratings versus live plus 7 days? Those are the questions. Here’s the answer: Yes. The Big 4 are failing because, as has been obvious for almost a decade, they must fail. Fragmentation and ad avoidance have killed their business model -- duh. Their inexorable downward trajectory will be interrupted only in outlier years, bumped by such things as the Olympics, close elections and the rare hit reality show. Meantime, the only ratings grabbers beyond competition shows will be sporting events and live awards programs commanding real-time attention. Period. That was true in 2005, when I first started saying it. It was probably true in 2000, before I started saying it. And it will be true until the shakeout begins, whereupon it will only be a question of whether any survive into the 2030s. Or 2020s. The tipping point will be when the law of diminished returns kicks in, which could be any day now. What has kept the nets afloat, paradoxically enough, is the very fragmentation that is decimating them. As the mass audience has gradually but enormously eroded, the value of any mass audience has increased all out of proportion to actual reach. It’s like the last gas station before Death Valley: $10 a gallon. The Big 4 have kept revenues flowing by doing nothing more visionary than gouging at the pump. But the traffic on the desert highway is now so light, even the gougers won’t long be able to keep their pumps running. That’s the simple economics of the situation. Even if the Big 4 had the wherewithal to produce the likes of Homeland, Breaking Bad, Mad Men, Girls, and Game of Thrones -- and for reasons of budget and FCC nannying they emphatically do not -- they would suffer an end-stage condition. But they can’t even program themselves into survivability, because the one aspect of their business model that stubbornly pertains is the sanctity of the lowest common denominator. The question, therefore, should not be how the Big 4 can cure what ails them. They cannot cure what ails them. The only relevant set of questions concerns what will succeed the Big 4. Is there a place for an all-live network? Is there a place for two? If CBS is a cable channel, what will it present? Cable channels are -- in varying degrees -- vertical. Comedy Central and Discovery have organizing principles, and therefore constituencies. CBS, NBC, ABC and Fox have no organizing principles. They have decades of brand equity, but literally zero brand meaning. They are, in short, irrelevant. They exist to sustain the affiliates, who in turn exist to sustain the nets in a sad symbiosis of mutual obsolescence. Advertisers aren’t served. Audiences aren’t served. The only thing being served is inertia.