Every person I've spoken to who visited Colombia warned of two things: 1) There is a very large homeless/beggar population in the cities, who prey on tourists. 2) If you like to explore countries beyond typical tourism, it's safer to do this with a native Colombian that you trust, who knows the dangerous places.

Oddly when I speak to Colombians, they refute both of these warnings every time. I'm not sure if it's a cultural thing to downplay danger or discomfort, but those are #1 on my travel priority list.