1) A generic name used just like john doe or jane doe. It is a "sample name"
2) A generic name for a tool or a village idiot. Most commonly a generic wigga especially one with a great deal of wiggerness, particularly in the Northeast near New York but well outside of any real ghetto.
teacher "I'm going to have to write you up, whats your name?"
student "John Sample"
Intercom "Will (the mutha Fuckin') john sample come to the office NOW!"
"dude, john sample is such a myth"
"No way, I buy all my drugs from him"
"LoL, ur never gonna be able to rat out ur dealer - he is a john doe"