Nope, nothing is certain, and some charities are more inefficient than others. The Royal British Legion spend £30 million last year of its £130 million income on expenses, but I would still always buy a poppy each year.
But not donating anything to the DRC/Red Cross/Oxfam does ensure that none...
Too right, I have a mate who can't afford Lambert and Butler any more, and has to roll his own, whereas these let of flipingellinos have loads of trees they can chop down to make homes out of.