Beyond being infuriating and insulting, President Obama's now notorious "you didn't build that" speech probably left many people puzzled. It is so foreign to how most Americans think they might have wondered where such thinking comes from.
Whether or not you think it's accurate to call Obama a Marxist, his perspective on how the economy works is Marxian through and through. More specifically, it is a reflection of what's referred to as Marx's "labor theory of value."
That theory is defined in the Dictionary of Economics as "[t]he worth of a product or service is in proportion to the labor employed to generate it."
Economists not under the spell of Marxism consider the labor theory of value to be a convoluted mess. Marx himself had great difficulty papering over the logical gaps and contradictions of the theory. One obvious problem is that "labor" is not a homogeneous resource. Furthermore, it is not the only scarce resource necessary for the production of practically every product or service
http://spectator.org/archives/2012/08/13/obamas-labor-theory-of-value