It’s too early to say for sure, but this spring’s TV ratings books indicate that viewership is on the verge of falling off a cliff. “Everyone has a theory to explain the plummeting ratings: early daylight saving time, more reruns, bad shows, more shows being recorded or downloaded or streamed. Scariest of all for the networks, however, is the idea that many people are now making their own TV schedules. The industry isn’t equipped to keep track of them.”