It may sound like I’m recommending that you “trust no one”, and that’s sort of true. What I’m really recommending is that you know who you’re trusting. When I received the “Jane Fonda” spam, it came from a friend who “received it from a very intelligent, reliable chemist,” and was taken at face value because of that. But the very intelligent chemist didn’t write it. Someone much less reliable wrote it, and the chemist’s reputation should not have applied without a further note from the chemist saying “I’ve checked this out, I believe it to be true. Here are my references.”
The same should apply to any news you receive from any source. Where is the information coming from? What value does this information hold? It doesn’t matter if you received it on Usenet or from the New York Times, the same questions and the same skepticism should apply.