hah Raevsky. of course visa can be cancelled. at the interview CO can DENY you a visa.
if you overstay your visa, for example, and come back to your country your visa, even though not expired yet, gets cancelled. another example. if you are in US on let's say J1 visa and try to change your status which is later denied your visa, even if still valid, gets cancelled. those are only two simple examples.
you try to pretend you know everything which becomes funny. "Colombians get visa for 10 years, true". Lol. They can get visa valid UP to 10 yrs. Doesnt mean all of them are given for such a long period of time. And that applies to every other country. You can get your b1/b2 visa for a year, two, three, five... 10. everything depends on your individual situation.