Its all very well going on about how the fuel is okay over here, but if you fly to a 'dodgy third world country' how do you know that you're getting decent stuff when you refuel? Once contaminated how do you get rid of it? Yes you can test for it once a month but with it doubling in size every 20 mins it doesn't take (potentially at least) long to cause a problem.
However, I doubt that there is a cover up and in the 30 odd years that I have spent in the industy I haven't come across many incidents. But if a particular airline was having a problem are they going to shout about it? I doubt it very much.
The aircraft manufacturers aren't going to make a big deal about it either as they won't consider it their problem. Unless of course they have used inferior metal in the construction of the wings.....