In Brazil, soap operas, and specifically the small families they depicted, might have been a form of birth control, lowering the fertility of the audience:
In 1960, the average Brazilian woman had 6.3 children. By 2000, the fertility rate was down to 2.3. The decline was comparable to China's, but Brazil didn't have a one-child policy. In fact, for a while it was even illegal to advertise contraceptives.
Many factors account for the drop in Brazilian fertility, but one recent study identified a factor most people probably wouldn't consider: soap operas (novelas). Novelas are huge in Brazil, and the network Rede Globo effectively has a monopoly on their production...
Using census data from 1970 to 1991 and data on the entry of Rede Globo into different markets, the researchers found that women living in areas that received Globo's broadcast signal had significantly lower fertility. (And yes, the study did control for all sorts of factors and addressed the concern that the entry of Globo might have been driven by trends that also contribute to fertility decline. I'll spare you the gory econometric details.) Additionally, people in areas with Globo's signal were more likely to name their children after novela characters, suggesting that it was the novelas specifically, and not TV in general, that influenced childbearing.
Update (by jkottke): The Sabido Method:
Named after the pioneer in application of this entertainment-education strategy, Miguel Sabido, the Sabido Method is based on character development and plot lines that provide the audience with a range of characters that they can engage with -- some good, some not so good -- and follow as they evolve and change. Sabido developed this methodology when we was Vice President for Research at Televisa in Mexico in the 1970s.
According to the Mexican government's national population council, a soap opera called Acompaname was responsible for large increases in people requesting family planning information, contraceptive sales, and enrollment in family planning clinics. From 1977 to 1986, when these soap operas were on, Mexico's population growth rate fell by 34%. The Sabido Method was also recently covered in the New Yorker. (thx, omegar)