McClatchy summarizes the long list of policies where President Obama has reneged on campaign promises—either in letter or spirit—and adopted the policies of his predecessor. We've covered many of them here, but they range from a broad application of the state secrets doctrine to invocations of executive privilege to the Defense of Marriage Act to a host of other issues related to transparency and disclosure.
My own hunch is that presidents try to keep campaign promises that expand the government and their own power, and either back down from or are unwilling to expend much capital on promises that make government smaller and more accountable, thus limiting their own power.
Looking over PolitiFact's report card on Obama's campaign promises, that seems to be about right thus far. By my count (and some of this is certainly subjective) of the of the 31 promises the site says Obama has kept thus far, 20 in some way grow or expand the federal government. Just six make the government smaller, more transparent, or more accountable. The remaining five have no effect, or amount to a wash.
Of the six campaign promises PolitiFact says Obama has unquestionably broken, five would have limited his own power, provided tax breaks, or provided more accountability and transparency to the federal government. One was mostly symbolic (recognizing the Armenian genocide). So far, he hasn't broken a single promise that would grow or expand the government, though he has compromised on a few, and many have been stalled.
PolitiFact also gives Obama more credit than he deserves on some promises. For example, Obama's promise that "Under my plan, no family making less than $250,000 a year will see any form of tax increase. Not your income tax, not your payroll tax, not your capital gains taxes, not any of your taxes," was broken when he signed a bill raising taxes on cigarettes to pay for an expansion of the SCHIP program. PolitiFact calls this a "compromise." But "not any of your taxes" seems pretty clear. Obama didn't say, "not any of your taxes, so long as you don't smoke" or "so long as you don't have habits the government finds distasteful."
In short, I think it's safe to say that Obama has been willing to spend plenty of political capital on his promises that vastly expand the size and scope of the federal government, and relatively little on promises related to eliminating waste, putting limits on his own power, or making the government more transparent and accountable.
It's worth emphasizing that this analysis isn't holding Obama to some libertarian standard of the ideal president—I'm not looking at how many of his total policies grow government versus how many limit it or hold it accountable. It's holding him up against his own campaign promises. That is, even when you assume the positions of left-of-center, big government Obama-the-candidate as your baseline, Obama-the-president comes up short.