There is something that has always bothered me about the thought experiments / intuition pumps that are the ultimate data for ethics according to many people, and for even more people, the rhetorical device driving ethical writing. Consider the following typical case (drawn from a pretty much random source):
You are out in a small boat and come upon fifty people in danger of drowning. Your boat can only accommodate ten people, and there is not time to make more than one trip to shore. Furthermore, there are no other boats in the area, and no one close enough to aid in any other way. No matter what you do, at least forty of the fifty will die.
My immediate inclination in these cases is always to try to find some way out of these situations. This, of course, is cheating, the ethicist will say. If you press them, they will add further constraints that frustrate your creative solutions, until you are left with the "hard choice" that the ethicist wanted to probe your intuition about.
I suspect my annoyance at this procedure is pretty universally understood as a sign that I am not serious about ethics, that I'm being annoying, or that I am too thick-headed to see the point. I also suspect that there is a strong pressure to stop suggesting the creative solutions, and to "play along" when these kind of cases are brought up, so that the ethics discourse can continue. And certainly, taking a certain conception of what ethics is to do for granted, this would be a totally reasonable way to go.
But I've still got a nagging bit of dissatisfaction, here, that I want to probe. Why do people react this way to thought experiments in ethics in particular? No one tries to "weasel out" of thought experiments in physics (do they?). I think my worries begin with a strong feeling that ethics ought to be tied to helping people make concrete moral decisions. I know this isn't universally accepted; it isn't uncommon to make a distinction between decision procedures and standards of value, to focus ethical theory on the latter, and to ignore any impracticalities of it, because those only matter for the former. I don't buy it; I think ethics has to be strongly concerned with both, and that they probably aren't totally separable. For a criterion in ethics to be true, it seems to me that a minimal condition is that it ought to be usable in (at least some) concrete situations.
Here's how I analyze my dissatisfaction. It seems like what I, or the undergrad ethics student, or others who cause this kind of trouble are trying to do is actually a sign of a good moral sensibility. It's not that we're not serious, or annoying, or thick-headed. It's that we're trying to do what most people try to do, what one ought to do when faced with a moral problem: we're trying to find a solution that maximizes all the types of value at hand. This kind of problem-solving activity uses a variety of resources, including background knowledge from any relevant area, to try to come up with a better solution than the immediately obvious ones.
Take the example above. As I read, I have in mind a picture of what my boat looks like (smallish wooden boat with oars), and I start using my background knowledge to come up with ideas about how we could save more people. Perhaps a few people could use the oars for flotation? Perhaps we could break up the boat and everyone could have a large enough piece to stay afloat? What if, instead of just letting 10 people in the boat, I let as many people as can manage grab on to the side to stay afloat? Etc.
And I start to think about reasons to take certain people over others. I should pick women and children, and probably I could fit more. I'd pick people who look weak or like poor swimmers, and try to come back for the others. Maybe I'd pick one or two stronger looking fellas who could paddle the boat faster than I could. And so on.
None of these considerations are supposed to be allowed, of course, because the point is that we want to theoretically explore the case when we can only save 10 out of 50. We want to ask something about our obligations, or their claims, or whether there is moral remainder, or whatever. They don't want the creative solution because it prevents us from facing genuine conflicts of value, which is one of the things they are interested in exploring. So the ethicist will keep adding stipulations until you are forced to deal with the issue that interests them.
And, given enough examples with this, you're probably going to get driven out of ethics, or you're going to fall in line. This actually strikes me as quite a vicious result! One of the results of studying ethics, then, is to squash one's ability to engage in ethical deliberation! No wonder that it's said: "nothing makes a man so much of a scoundrel as a prolonged study of ethics". In this case, we should recommending to students who might hope to become more skilled at solving moral problems, or become more reflective about right-behavior, to at all costs stay away from Ethics courses!
A further worry goes to the heart of the enterprise. I think the most sensible way to understand the point of intuition-pumping must be that it is supposed to make explicit the wisdom implicit in our practices of ethical choice-making, or, a bit more opaquely, to find out our core commitments or basic beliefs at the level of particular judgments. There is a worry, though, that since, in the course of intuition-pumping, we actually end up pretty far away from normal practices of ethical problem-solving, that whatever the thought experiments produces is going to be loosely if at all related to any actual implicit wisdom we have or practical judgments that we would make.
 It is quite difficult to find the original source of this saying. I've seen it alternatively attributed to C.S. Peirce and G.K. Chesterton.