In US television, "the censors". In the early days of the medium there was no Hays Code as there was in motion pictures - the individual networks did their own policing of content. It probably wasn't hard work; writers and producers complied without any problems. On I Love Lucy, Lucy was never "pregnant", she was "expecting" or enceinte. Plus all married couples slept in separate beds. Then where do babies come from? Well, there weren't many pregnancies in US TV back then; only Little Ricky comes to mind.

The fun really started during the Vietnam War. The Smothers Brothers Comedy Hour had its own little ongoing war with S&P at CBS (as did, to a lesser extent, Laugh-In at NBC), with sketches that had political, sexual, or drugual content never before seen on the small screen. Their success opened the door for the taboo-breaking of the 70s: politics was a big part of All in the Family, some detective shows tried to squeeze in as much grit and realism as possible, and Saturday Night Live stretched the boundaries of what you could say and do on TV after the kiddies were put to bed. And now, instead of censoring a word here, or a situation there, whole programs became bones of contention: Maude did an episode on abortion, for instance, and an anti-war drama, Sticks and Bones, almost never got on the air. In a compromise, NBC allowed the title character of James at 15 to lose his virginity only if the show's name was changed to James at 16.

In more recent years, as the networks lost viewership to cable television, S&P was allowed to loosen up further; shows like Married with Children and NYPD Blue (by Steven Bochco, a veteran of many censorship battles) would never have gotten on the air, once upon a time. Other shows were able to fit a "penis" here, a "bitch" there, into dialogue. Sexuality was touched upon in a franker manner than in the past (partly a result of the rise of AIDS awareness), a far cry from the somewhat chaste romance of 50s/60s (and even a lot of 70s) TV, but still a far cry from late-night premium cable. It opened up a new industry for people who felt the networks had dropped the ball - i.e., the Don Wildmons and Brent Bozells of the land, self-appointed culture warriors, who used the uncensored airwaves of Pat Robertson, Jerry Falwell, et al, to stir up "grass roots" support for protests and boycotts.

And this is, still, only the beginning. There remains seven words you can never say on television. And a lot of stuff you still can't do on Fox.