Good freaking question! "Oh snap" can mean "Damn it," but it's not quite as strong. "Oh snap" can also be used when you remember something. For example, if I suddenly remember that I have a date with a beautiful girl I can say to my friends, "Oh snap! I totally forgot! I have a date with a hot chick tonight!" Another common usage is to express happiness. If I see my friends while I'm walking down the street I might say "Oh snap! Look who it is! Big, bad Brandon!"

in a way, yes... - a playful indication of surprise, misfortune, or insult http://www.urbandictionary.com/define.php?term=oh+snap :)

out of frustration