The name comes from the fact that many businesses make gains for their yearly profits, putting it in the "black" ink as opposed to the red ink, which they often operate on in the months preceding Black Friday.
Another theory or application of the name is that in a sense it is the exact opposite of Black Tuesday, in that the retail economy booms as opposed to collapsing as it did in 1929 on Black Tuesday.
Guy2: Fuck no, man, do I want to get trampled by a crowd of people trying to buy a cheap Xbox?
yet another example of how greedy americans are.
Zach: No way, man, it's Black Friday.