Occasionally it seems to work out, more or less. That's where the temptation arises. Yes, usually a bad gamble. But what choice do you make when all your choces look like bad ones?
It is one of the dilemmas facing an ethical and moral being when confronted with such situations. So, we have to choose very carefully and not let charlatans like Chalabi take advantage of us. Let me illustrate with an example. In Afghanistan, we had to choose between the bad old Soviets and the mujahideen. Bilking us were Pakistan (as it still is), Gulbuddin Hekmatyar, Osama Bin Ladin, all three of whom we supported to some extent or the other. This was thanks to the CIA (guys like Milt Reardon and Anderson) who gave Reagan cause to believe that the above mentioned three could kick the commies out the fastest.
That was a horrible mistake. We should have chosen Ahmed Shah Massoud instead.
This is how we always screw up. We chose the most expedient path, not the most viable long term one. We choose corrupt manipulators who say what we want to hear, and who turn against us when their goals are acheived.
Such as Chalabi, who lied to us about the WMD's, and is now in cahoots with Iran.