Lyric discussion by mtalinm 

It's about the 2008 financial crisis in general, and the TARP bailout in particular.

The "angels" are the 99% (i.e., working folks) and the "shameless" protagonists are the bankers who caused the mess by "standing on the backs of angels" and "feed[ing] off the machine"

"tears fall from the shameless" is a reference to the crocodile tears of the heads of JP Morgan etc looking for federal bailout money. that's the "shelter me, guide me to the edge of the water" (i.e., get me to safe land.

The selfless/righteous angels are "burdened" with the bailouts because their taxes pay for it all.

...

I'm quite sure this is the main reason it was nominated for a Grammy. Wall Street is perhaps the one industry Hollywood fancies itself more noble than.

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