The flip side, however, is that spectrum is required to compete with these companies. The big telcos might not be too keen on shelling out $X billion at the expense of next quarter's profits, but if buying that means that Rival Startup Inc. can't get any spectrum at all? They just cemented their profits for the forseeable future at very little relative cost.
Given that there his established historical precedent for companies buying up spectrum and letting it languish (see: Verizon's purchase of the 700mhz block A spectrum) and increasing evidence that spectrum availability isn't the limiting factor in cost for the big telcos (it's increasingly looking like subpar infrastructure is to actually to blame, if anything), it's fair to assume that these companies are willing to employ this strategy.
The duty of a regulatory agency like the FCC seems clear: Ensure the market remains fair and that competition works in favor of the taxpayers. Don't sacrifice that for what seems a short term gain, because the amount of gouging that happens when the market is locked up without competition will be far higher.