Karma is a bitch, really?

We often prophesy that KARMA will catch up on people for whatever it is they have done, wrong or right.

It got me thinking, where did that belief come from?Then I read that it is a Buddhist belief that whatever you do comes back to you. See, I'm not one to take things on their face value alone or believe something just because people say so, I like to analyse until it makes sense to me (that might not always be a good thing, I know).
So, when I hear people go on and on about karma, even those that do not believe in Bhuddist traditions somehow believe in the existence of Karma, I wonder how does it really work?

For instance, A hurts B, C hurts A, people believe that C is A's Karma (you get the link?). I wonder, what if A is B's karma? why should Karma visit A again for doing its work?  

I see a lot of bad people moving around, having a swell time, while the good people continue to suffer (please don't tell me about their reward being in heaven). If someone does something bad, and the children suffer after he/she had died, will you say that Karma has dealt with him/her? He can't even feel it! 

Okay, rant over. Back to work, Nneka!! 

Hugs...