But would you trust math olympiad performance over good grades in graduate level math courses? What about publications in respected math journals? If by the time you graduate from college your math olympiad scores are the best things you have going for you, you've got a problem.

Yes, I would take math Olympiad performance more seriously than graduate level math courses.

As for publications, that would depend on where the paper is published and how much of a contribution was made by the candidate vs his/her coauthors.

IQ doesn't change much. If you were super bright in high school, you will probably still be super bright in your 20s and 30s.

But it takes more than a scalar score on a test to prove your ability to integrate whats around you into something new. If you get a perfect score on one of those tests and don't do jack shit afterwards, what does it mean?

I wouldn't trust either. Jumping through hoops doesn't cut it. Do something unforced that is exceptional.

How is the math olympiad forced?

I meant that it is more impressive to find and solve a solution to a novel or significant problem than jumping through a difficult set of solved insignificant problems. Forced in this sense means that someone has framed where your mind has to go; you don't have to recognize and make value judgments on it's worth.