A recent report from Barclay's Wealth (PDF) addresses the concerns of wealthy philanthropists, and why they may be less so. There is a study on why it is those that donate do so. The top reason, "I can afford to." Religious beliefs came in at number 10 (though it came in on top as an "internal motivator." The study concerns the UK and US. It would not make much sense to do a study this way except that Barclay's is a British Bank, and so the numbers may be a little skewed.
The results however were bad overall. Most wealthy people donated less then 1% of their net worth every year, indicative of hoarding, only 1/3 gave more. The economy is not the main reasons the wealthy hold back, though its a factor. Tax policies, how charities are run and the lacking of key motivators are also to blame. Trusts and Estate Magazine summarized the report here (subscription required).
