The idea is simple enough - air rudimentary on-screen word or number games, invite viewers to call a premium-rate line with the answer, then sit back and rake in the cash. As NTV suggests, the craze is sweeping European TV—Germany’s not alone, just surf the hotel TV channels next time you’re on this continent’s shores—as networks look to replace falling broadcast ad revenue. ProSiebenSat.1’s call-in subsidiary 9Live processes 240 million such calls annually, generating Q1 revenue of EUR 28 ($37) million, while the parent expects the format to account for 14 percent of its revenue by next year, the article says.

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But, if the UK response is anything to go by, the quiz call format is a shaky revenue source. Scandal after scandal has dented confidence in the genre - from quiz questions so simple they can be considered a lottery, to callers having almost no chance of getting picked to appear on air, to shows outright rigging the results of games, the outcry has prompted regulatory reform, as Giles Crown of UK law firm Lewis Salkin explains, and led broadcaster ITV to take its dedicated ITV Play quiz channel off air. Suspicion about this brand of interactive TV is growing - NTV links to a 1,000-member forum at which German viewers coordinate online detective work by posting inside info and complaints exposing perceived transgressions. If the UK’s recent episode prompts regulatory aftershocks, European networks might want to check they are operating on the right side of the law before betting the bottom line.

Rafat adds: U.S. is still behind in this one, with American Idol being held as the biggest example of TV interactivity. And of course regulatory rules are very different here, and so are the cultural habits of TV watching.