From my experience, Karma and "What goes around, comes around" are real. It is also evident that Ayn Rand incorporated her belief of them in The Fountainhead. Apathy and cruelty (as well as carelessness, paranoia, hubris, etc.) tend to retaliate, while being noble and generous pays back in spades.
I decided that if someone asks me for me money, I will give them up to a reasonable amount (e.g: the resentful beggar case, or the story of my first kiss ).