I will allow some leeway room -- I have no issues believing that CHILDREN receive signs. And the reason I say that is because (unless instructed by someone else) they're not doing it for nefarious purposes (scamming, manipulating others, etc.). They are also closer to Heaven, in the sense that they are not as tainted by the influences of earth; think babies and how they're able to perceive auras. I believe the more time we spend on earth, the more we lose our heavenly gifts.
But as for adults, it is more difficult. Obviously there were prophets in the Bible, ones chosen by God to receive His word. But herein lays the problem with choosing to believe adults: adults have ulterior motives, and they can lie by CLAIMING to be chosen by God. There are many instances where TV mediums have been able to infer personal details about a person's life just from the context clues they give. When it comes to instances like this, I prefer to simply listen to the Bible as opposed to taking chances...
RE: We Should Practice What Is Preached