Once you start to notice them, they're everywhere.
The streets of New York are covered in literally millions of small black marks where people have discarded chewing gum that no longer has any flavour. The density of the spots is particularly unnerving in the subway stations. Just how long does this stuff last?
I've seen little men valiantly attempting to clean up the debris using high pressure hoses. Their machine seems to be reasonably effective, but the sickly sweet smell that it unleashes is equally frightening. Presumably the gum that is prised off the pavement is sent to some god-forsaken landfill to while away eternity next to a myriad plastic bags and nappies.
Given the longevity of the little skid marks, I hate to think what happens if you accidentally swallow some gum.