Is my karma going to hell because I hang up on charities that phone me asking for money? I always feel a little bit bad for doing so (which happens about once a weekend), but I logically I know I really shouldn't. If everyone donated money to every charity that ever called them, then charity cold calling would just explode and everyone's phone would be continually ringing. The amount of money these charities received would probably increase at first but then fall back to normal levels as people found themselves having to donate smaller and smaller amounts per phone call.
On the other hand, if no-one ever donated money to charities that called them, the calls would soon stop, the people employed to make the phone calls would be able to put their energies towards more constructive uses (such as promoting that charity's cause in less invasive ways, or working more directly to help the people that the charity is trying to help) and I could go back to expecting to speak to family or friends whenever I heard the phone ring.
I figure the best thing to do with charity phone calls is just to hang up as quickly as possible (without even saying anything) after discovering that it's not somebody I know or some kind of emergency. That way I have used up as little of that charity's money/time as possible (not to mention my own valuable time). Doing this feels kind of rude but it really isn't - the call in itself is rude so the social contract of politeness has already been broken and there should be no expectation of politeness from me.
I'm not against the concept of charity altogether (I donate money through work so it gets taken out of my paycheck before the tax withholding, my employer matches my contribution and I don't have to remember what I donated when I come to file my taxes).