Betteridge's Law of Headlines

From the Wikipedia

Betteridge's law of headlines is an adage that states: "Any headline that ends in a question mark can be answered by the word no." 

It is based on the assumption that if the publishers were confident that the answer was yes, they would have presented it as an assertion; by presenting it as a question, they are not accountable for whether it is correct or not. The adage does not apply to questions that are more open-ended than strict yes-no questions.