Paper & Proof from Genealogy Tip of the Day

I read this post, Genealogy Tip of the Day: One Piece of Paper Isn't Proof, the other day. And while I don't disagree with his premise, my contrary nature requires me to ask - How many pieces of paper are enough? What if there is only one piece of paper? Are researchers required to treat everything they find like it might be a double-agent from the underworld purposely sharing compromised intelligence?

I understand that all people at all times make all sorts of mistakes filling out forms and remembering the past. I also know that people, in the past and now, purposely try to hide information, like illegitimate births and bigamous marriages. It is important to be aware that information you find might be incorrect. But on the other hand, it might not be. Seriously. You might actually find something that is correct.