So I guess the real question is, for those of you who believe Uber should behave this way (and, w4, I recognize that you're merely explaining modeless's argument, not claiming you agree with it), do you believe Uber should be expected to behave this way, given that they are a for-profit company, or do you believe that it is merely the *right thing to do (for some ambiguously-defined moralistic definition of "right")? I suspect that what you really believe is that it's what you personally think should happen, because it would result in lower surge prices for the same supply, and you would like to pay less money. And that's not a very compelling argument.
Imagine for a moment that surge pricing were kept the same. The only difference is that, now, Uber takes no cut whatsoever. This would result in greater profits for Uber's drivers during a surge, better incentivizing drivers to get out on the street and start accepting fares. This increase in the incentive would, one can assume, result in an even greater increase in supply during a price surge than is produced under the current system, and more effectively address the supply and demand imbalance that creates the need for surge pricing in the first place.
Now, does Uber have a moral obligation to do this? Fuck no. However, it's certainly disingenuous to suggest that surge pricing is just all about addressing supply and demand imbalances.
(I'm not saying you say that's what it's all about; you don't. That is, however, what wutbrodo and a lot of other posters seem to be suggesting).
EDIT: As an aside, Uber's incentive (besides defensibility) for not taking a cut of the surge is clear: by making the incentive for drivers to get on the road as powerful as possible, Uber would all but guarantee that its users can get a ride at any time, any day, in any conditions. That would solidify Uber's primacy over other, less reliable transportation options. However, given that their product is already so superior to the alternatives, it doesn't seem to be the case that they need to look at doing anything like that for the time being.
Whether or not that is feasible under Uber's business model is, of course, a totally different question.