My interest in moral dilemmas was "tickled" recently, when I had heard a religious person stating that "stealing a dollar from a rich person is not as bad as stealing it from a poor one". Now, my reaction to such a statement in any other setting would be to ask a few follow up questions, but in this case, what struck me the most is the fact that the statement came from someone, who would be the first one accusing others (especially non-religious) of moral relativism.
In my mind, if we do not have any additional information, the question is simple to answer: there is no difference, when you are stealing from poor, or rich. A theft is a theft and, since your actions cause harm (physical, or mental) to others, they are morally wrong. We can, of course, expand this problem, by introducing variables, like your own wealth, or your current situation (Les Miserables comes to mind), and such differences can considerably change the outcome.
In any case, the answer might never be as obvious as one would expect, but my surprise was not so much with the problem itself, but with the person who stated it and "solved" it using some pretty relativistic criteria.
To follow up, here are some interesting readings on various moral philosophies and dilemmas:
1. Moral Dilemma: Would You Kill One Person to Save Five?
2. Stealing from the Rich
3. On ethics, part I: Moral philosophy’s third way
4. On ethics, part II: Consequentialism
5. On ethics, part III: Deontology
6. Of trolleys and morality