poltroon - someone who uses the anonymous nature of an online forum to hide their true intent.
Posting to a Bicycling Travel Forum:
"Searching Far And Wide For Cycling Companion.
Be everything as it may, this transcontinental, international cyclotouriste is navigating to locate a good companion for an extended bicycling tour. Good is defined as---female, healthy, cyclist, with a sense of bold adventure, and the willingness to be compatable on an extended world tour with yours truly."
When in fact this very person claims to have predicted (and declared to the world in a park in Florida) the 9/11 attacks and is just looking for the opportunity to tell you that ... what a poltroon.