Poor Obama

OK, so all of the nominees for Commerce, Health and "Chief Performance Officer" for the US government have tax problems, severe enough to cause two of the three to withdraw (so far). As Oscar Wilde's line about lost parents goes, one is unfortunate but two shows carelessness. It would seem to be impossible (i) to get to Washington DC without being pretty darn well-off and (ii) to actually pay all your taxes once you're pretty darn well-off. Is this a problem with a highly-complex tax system or a more basic issue of greed?