You might be able to persuade more people to give by talking about what isn't than by telling them what is.
A recent study, reported at the Neuromarketing Blog, looked at the impact of "counterfactual reflection" -- visualizing what would have been: Build Loyalty like George Bailey.
Subjects were asked to reflect on how the US came into being. Half of the subjects were asked to reflect on what their world would be like if the country hadn't come into being. (This is called "counterfactual reflection.") The other half were told to think about what their world is like because the country did come into existence (factual reflection). The subjects who were told to imagine the "what if the country hadn't come into existence" scenario demonstrated higher levels of patriotism in subsequent testing than those that reflected on their actual situation.
Counterfactual reflection comes naturally into charity conversations. Especially when we thank donors, we should be very clear about what things would have been like without their gift.
But probably more important is how you ask in the first place. Most nonprofits put a lot of energy into proving their value by describing the good they are doing. It would be more effective to help the potential donor see a world without their work. Unsolved problems. Unmet opportunities.
This is also why bad news raises more funds than good news.
Find the original study here.