My beef is not that we believe what happens, my beef is that we believed what happened before we had reason to believe it. …Friends, we are to be slow to believe evil reports. We are to wait until there are two witnesses, that is two witnesses who will stand up and say, “I noticed.” Or at the very least we are to wait until the person confesses.
You can read the original post for more of the biblical foundation for this claim, but I agree with it. One very troubling trend I see on twitter and facebook is a sort of forced credulity, a habit of accepting lone anonymous sources lest we should inadvertently allow some evil to continue.