Okay, this is getting annoying. I've mostly ignored "near vs. far" topics because I don't know what the metaphorical meaning of the two is. Then, when I went to the LW wiki to be enlightened so I can understand these topics, what do I get?

NEAR: All of these bring each other more to mind: here, now, me, us; trend-deviating likely real local events; concrete, context-dependent, unstructured, detailed, goal-irrelevant incidental features; feasible safe acts; secondary local concerns; socially close folks with unstable traits. FAR: Conversely, all these bring each other more to mind: there, then, them; trend-following unlikely hypothetical global events; abstract, schematic, context-freer, core, coarse, goal-related features; desirable risk-taking acts, central global symbolic concerns, confident predictions, polarized evaluations, socially distant people with stable traits.

So ... one of them goes with a bunch terms that have some vague relationship to each other, and the other one ... um, does the same with different terms. Was that supposed to somehow be helpful?

Anyway, I don't know how to translate this into near and far, but here's my answer to the trolley problem:

Workers on the track consented to the risks associated with being on a trolley track, such as errant trolleys. (This does NOT mean they deserved to die, of course.) Someone standing above the track on a bridge only consented to the risks associated with being on a bridge above a trolley trolley track, NOT to the risk that someone would draft him for sacrificial lamb duty on a moment's notice.

By intervening to push someone onto the track, you suddenly and unpredictably shift around the causal structure associated with danger in the world, on top of saving a few lives. Now, people have to worry about more heros drafting sacrificial lambs "like that one guy did a few months ago" and have to go to greater lengths to get the same level of risk.

In other words, all the "prediction difficulty" costs associated with randomly changing the "rules of the game" apply. Just as it's costly to make people keep updating their knowledge of what's okay and what isn't, it's costly to make people update their knowledge of what's risky and what isn't (and to less efficient regimes, no less).

That is what differentiates pushing a fat guy off, from diverting one track to another. I don't pretend that that is what most people are thinking when they encounter the problem, but the "unusualness" of pushing someone off a bridge is certainly affecting their intuition, and so concerns about stability probably play a role. And of course, you have to factor in the fact that most people are responding on the fly, while the creator of the dilemma had all the time in the world to trip up people's intuitions.

This is not to say there aren't real moral dilemmas with the intended tradeoff. It's just that, like with the Prisoner's Dilemma, you need a more convoluted scenario to get the payoff matrix to work out as intended, at which point the situation is a lot less intuitive.