When Karl Marx wrote Capital in 1867, he said capitalism would never be able to get rid of credit bubbles, financial crises, high unemployment etc. He said that over time the problems would get worse and worse with greater and greater financial crises. Here we are about a century and a half later and you just have to look at the housing bubble, the bank crisis, TARP and the government bailout, unemployment in the US and Europe and the Arab countries which helped cause the Arab spring to see how prophetic he was in this respect.
Marx and Engels wrote that the world has seen five economic systems. Each system collapsed due to internal contradictions. The first system was hunting-gathering, then Babylonian/Greek/etc. style slavery, then feudalism, and then capitalism. They saw the Paris Commune as the harbinger for the next economic system which would replace capitalism.
The central contradiction in capitalism Marx spells out clearly in Capital, although its a little too much to explain in a comment. Basically workers create $240 of wealth every eight hour work day, but are only paid $200 a day. The $40 goes to profit, to get more capital, to make more commodities. But what is happening here - the worker is shorted $40 a day, and what happens with that money is commodities are made. Who are going to buy all these commodities when workers are not getting all the wealth they create? Well credit fixes that in the short term but creates a bigger long term problem.
The communist manifesto says "the commercial crises that by their periodic return put the existence of the entire bourgeois society on trial, each time more threateningly". I certainly feel this way. So apparently does Stratfor. On this point, the left and right are in agreement.