I think the sense of entitlement from a donation is unbounded, since it was voluntary. People are usually more clear that a business transaction is thing x for money y.

If you're pointing out that people are acting irrationally, then, yes, they are. The difference is that we tend to treat "business transactions" different from other kinds - I think monetary donations are not seen as business transaction, so the expectations are different. See this excerpt from Dan Ariely's Predictably Irrational: http://www.npr.org/templates/story/story.php?storyId=8923395...