First of all, there is a consistently reported phenomena involving a shadow entity in an old styled hat. Then there is a phenomena involving a shadow entity whereby eyewitnesses often mention a "Fedora" or similarly brimmed hat. The latter is the scarier of the two and actually, the plain hatman doesn't seem to bother or upset most people who report an encounter.
The plain hatman sort of acts like a ghost and is often seen just standing around. Its form may simply fade until the eyewitness no longer sees it, and it has no apparent reaction to people. For example, people have reported 'coming upon' this shadow person shape and having the shadow do absolutely nothing for seconds of minutes, then it may move around a bit and just fade away, as if it can't detect the person who came into the room and just saw it. This form of shadow entity is often thought to be the same as a ghost by those who study this phenomenon. It looks sort of like a ghost, with the shape of a person who is wearing an old style - always an old style - hat. Unlike a ghost, however, whose facial features you might be able to see, the plain hatman shadow person is a dark shadow with no detailed features. Just the shape. Its shape may not be well defined, but is definitely "person-shaped."
The above details of a plain hatman are not the sort of hatman that people are worried by. In fact, the above sort of hatman is one of the most common that is sighted and many people just think the encounter is a rather 'curious' event.
The other type of Hat Man terrifies people in every instance of an encounter. Also, this other type of scary encounter always mentions a distinct kind of hat, too - a Fedora-styled, brimmed hat. This type of Hat Man is the kind that people like Jason Offutt (author of "Haunted Missouri" and "Darkness Walks: The Shadow People Among Us.") and other researchers are trying to find out more about.
Here's an interview that Stephen Wagner at About .com did with Jason Offutt:
Another researcher of paranormal and UFO encounters, Heidi Hollis, founder and director of the paranormal and Coast To Coast AM discussion group, UFO2U, has interesting but very COMPLEX explanations for Shadow People which are wrapped up in theories about Reptilians, the Reptilian Agenda, etc. Whether or not you buy the idea or not that we might be just a whole world full of deceived people, losing our critical thinking abilities, so that an ancient Reptilian Race can put their Agenda forward (to have total control of all the world), Heidi's thoughts on the matter of Shadow People are interesting:
Heidi Hollis says that in order to deal with Shadow People we need to: