The gay girl in Damascus, it turns out, is an American male, married blogger. Yet prior to the story of the so-called 'arrest' of the blogger, few people doubted her existence. Most of us trusted that the information on the blog was truthful, despite the fact that invented personas in blogging are quite common. The question of how far we trust information received through testimony has been the subject of intense debate, both in cognitive science and in social epistemology. Of course, nobody argues that people do not (or ought not) rely on testimony; that would open the door to an untenable form of skepticism. But clearly, people aren't blindly credulous either - we exhibit some form of epistemic vigilance, especially when the information is surprising or improbable. But the precise degree to which we are credulous or epistemic vigilant is still a matter of debate.
Some authors, like Dan Sperber and Hugo Mericer, argue that people have evolved psychological mechanisms for epistemic vigilance to ensure that our reliance on testimony does not become disadvantageous. On the other hand, Paul Harris argues that trust in testimony is the default stance, and backs this claim up with psychological studies that indicate that young children (and sometimes also adults) do not even remember if they learnt something first-hand or through testimony (the well-observed distortion of eye witness accounts by posing leading questions is a good example of this). I am inclined to think that the fact that most people took the gay girl in Damascus story at face value lends support to the second position.
As Dan Sperber and his commenters pointed out, the question of our reliance on human testimony was already considered by David Hume and Thomas Reid, and both seem to be precursors of current positions in cognitive science.
David Hume seems to have been in favor of the position that we are vigilant in matters of testimony [quoted from his An Enquiry concerning human understanding]:
"88. ...there is no species of reasoning more common, more useful, and even necessary to human life, than that which is derived from the testimony of men, and the reports of eye-witnesses and spectators. This species of reasoning, perhaps, one may deny to be founded on the relation of cause and effect. I shall not dispute about a word. It will be sufficient to observe that our assurance in any argument of this kind is derived from no other principle than our observation of the veracity of human testimony, and of the usual conformity of facts to the reports of witnesses. It being a general maxim, that no objects have any discoverable connexion together, and that all the inferences, which we can draw from one to another, are founded merely on our experience of their constant and regular conjunction; it is evident, that we ought not to make an exception to this maxim in favour of human testimony, whose connexion with any event seems, in itself, as little necessary as any other. Were not the memory tenacious to a certain degree, had not men commonly an inclination to truth and a principle of probity; were they not sensible to shame, when detected in a falsehood: Were not these, I say, discovered by experience to be qualities, inherent in human nature, we should never repose the least confidence in human testimony. A man delirious, or noted for falsehood and villany, has no manner of authority with us.
And as the evidence, derived from witnesses and human testimony, is founded on past experience, so it varies with the experience, and is regarded either as a proof or a probability, according as the conjunction between any particular kind of report and any kind of object has been found to be constant or variable. There are a number of circumstances to be taken into consideration in all judgements of this kind; and the ultimate standard, by which we determine all disputes, that may arise concerning them, is always derived from experience and observation. Where this experience is not entirely uniform on any side, it is attended with an unavoidable contrariety in our judgements, and with the same opposition and mutual destruction of argument as in every other kind of evidence. We frequently hesitate concerning the reports of others. We balance the opposite circumstances, which cause any doubt or uncertainty; and when we discover a superiority on any side, we incline to it; but still with a diminution of assurance, in proportion to the force of its antagonist.
89. This contrariety of evidence, in the present case, may be derived from several different causes; from the opposition of contrary testimony; from the character or number of the witnesses; from the manner of their delivering their testimony; or from the union of all these circumstances. We entertain a suspicion concerning any matter of fact, when the witnesses contradict each other; when they are but few, or of a doubtful character; when they have an interest in what they affirm; when they deliver their testimony with hesitation, or on the contrary, with too violent asseverations. There are many other particulars of the same kind, which may diminish or destroy the force of any argument, derived from human testimony"
Thomas Reid, on the other hand, argued that trust is the default stance in matters of testimony: It is evident, that, in the matter of testimony, the balance of human judgement is by nature inclined to the side of belief; and turns to that side of itself when there is nothing put in the opposite scale ... In a word, if credulity were the effect of reasoning and experience, it must grow up and gather strength, in the same proportion as reason and experience do. But if it is a gift of nature, it will be the strongest in childhood, and limited and restrained by experience; and the most superficial view of human life shows, that the last is really the case, and not the ﬁrst (Inquiry into the human mind, 1764).