Which is exactly why today's media, according to the laws, have to publicly disclose such things. Thanks to our friend, Orson Welles.
Jonathan Crossfield has been providing some great facts and summaries of this situation. You may want to read #4 of this post where he eloquently explains why the Orson Welles thing is certainly no support for the people who think that writing fake content is a good way to get links.
In fact, I'll paste it here as well:
Orson Welles never planned the dramatisation as a hoax. He never intended for the audience to believe the radio broadcast was real and was horrified when he heard of the mass hysteria it caused. Welles used the news announcer format purely as a dramatic device for only the first half of the play, before switching to a traditional dramatic style that clearly revealed the fictional origins. Sadly, many listeners had already fled their homes by this point and were unaware how the play resolved.
People armed themselves. Farm silos and water towers were shot at. Panic was widespread. Are these things to be considered valuable or lamentable?
The backlash to the play was massive and overwhelmingly negative. CBS forever changed its dramatic guidelines to prevent such a thing reoccurring. Welles narrowly avoided punishment but was still censured for his involvement.
If this is to be held up as an example of how hoax news stories have valueŁ, then it quite clearly indicates the opposite.