The higher level you go, the less incentive there is. Take things down to a much lower level. For instance consider the ImClone insider trading case. Martha Stewart was a well known (among certain demographics) television personality, was on the board of directors of the New York Stock Exchange, and more. She risked, and lost, all that and ended up going to prison for acting on inside information. Her total gain was $45,673...

I think it's easiest to logically consider everything in reverse. Let's assume you're correct, that this sort of thing never happens. So that entails two possibilities. The first:

- No reporters, or individuals with the ability to influence what is written, have vested interests.

I think the above can be pretty easily dismissed as false. But if it's false we can assume at least some people have vested interests. Which leads to the next possibility:

- Those with vested interests choose to never actively utilize their position to further their interests

And again, I think we can pretty safely declare that's false. So it's not a matter of does it happen, but to what scale it happens. And that is going to be pure speculation. Although it would logically follow that the more people that a vested interest in event x, the more common the occurrence of biased media in favor of provoking x would be expected to be seen.