It's a funny world. NBC anchor Brian Williams lied about a matter of no significance, in an excess of boyish braggadocio, though in doing so he injured his credibility and, more importantly, that of his employer, NBC. We demand truth of our journalists and so Williams' suspension is as justified as the Schadenfreude at his come-down is not.
Journalists are expected to tell the truth. President Obama, however, lies regularly and reliably about matters of great significance and gets away with it. Part of it is that politicians are expected to lie. Obama does not disappoint, taking mendacity to unheard-of levels. There is a brazenness about it that has one admiring his cojones if nothing else. Another part of it is that politicians are not subject to the discipline of the market in the way news anchors are. Loss of credibility reduces viewership which reduces profits. That's the real bottom line, not the expectation of truthfulness.
(By the way, that is not a slam against capitalism but against our greedy fallen nature which was greedy and fallen long before the rise of capitalism. Capitalism is no more the source of greed than socialism is the source of envy.)
Here is a recent instance of Obama's mendacity.
Obama is a master of mendacity in the multiplicity of its modes. There is, for example, bullshitting, which is not the same as lying. Obama as Bullshitter explains, with a little help from Professor Harry Frankfurt.
There is also the phenomenon of Orwellian Bullshit.
Pelosi's Orwellian Mendacity: A STFU Moment documents, wait for it, Nancy Pelosi's Orwellian mendacity.