I've often found listening to American 'ghetto slang' fun, as they're always coming up with new vocab to replace over-used and over-popularised words; one outcast that springs to mind is 'whack' and of course there's ones like 'cool' and 'dope' which won't die, though you won't hear many that are 'cool' using that terminology anymore.
I have the feeling those who pioneer these usages adapt their language away from the main stream for the very reason Josie pointed out; so most will find them harder to understand.