Stuff often looks trivial - in retrospect. But it's not the only logical way, just a good way. It breaks down or does odd things in some cases (this is why the whole field of 'cooperative game theory' exists, because this sort of thing is not that easy).

For example, how would you divide up entropy, one of the most fundamental and scarce resources we possess? Shapley seems to work but there are some troubling parts: http://lesswrong.com/lw/12v/fair_division_of_blackhole_negen...

Does it work with all division problems, such as when agents can inspect each other's source code/rules? http://lesswrong.com/lw/13y/freaky_fairness/ and http://lesswrong.com/lw/3pv/freaky_unfairness/