Eh, this is one of those "grey areas" that are just going to have to wait and see on.
Technically, the gymnasts of China are whatever age is listed on their passports -- which is 16. It would take a number of things to happen for the IOC to do anything about this. They don't even have to act on a protest from the USOC. They can basically tell them to buzz off.
The problem they face is this: If they suddenly decide to investigate the matter of the Chinese gymnasts, they are going to infuriate China, regardless of whether or not they are 16. If they ARE 16, the Chinese have legitimate reason to be outraged. But let's be honest here, those girls look all of 14, if that.
It's potentially worse if they actually find something. Because then not only do they have to deal with the tarnish of one of it's premier sports (womens' gymnastics are among the highest rated events at the games), you then have to decide whether or not it's a disqualifying offense. Strip the gold from the Chinese, and you would see mass protests, boycotting, and demands from the PRoC to test every single American athlete who stands above China on an Olympic podium. This would cost the IOC dearly, both to investigate, and in potential revenue lost from outraged Chinese viewership (this would hurt more in the 2012 games rather than now).
And if you don't pull the medals, you essentially have every other competing country now rightly pissed off (USA, Romania, Russia, Japan), basically any country that was affected by the Chinese and their routines would have reason to openly protest the results.
To add to this, the longer the IOC waits, the longer China has to cover up any potential evidence of tampering.
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I'm not even as upset about the gold medal in the team all-around. The US women were not on form that night, and even Shawn and Nastia hit a couple of off-beats. My beef is with inflating Chinese scores.
If you actually go back and watch the tape of the gymnastics (this is for you, Firebat), you'll notice that during the individual all-around, the head-supervisor for the Gymnastics Committee of the IOC walked directly up to the judges and told them to lower one Chinese score, and raise one Russian score. She also said something very pointed and direct after one of the American routines (I believe it was after Shawn Johnson's excellent beam routine). Normally when a supervising official makes a trip over to the judges stand, she is either A) requested for a scoring clarification on a replay or B) being consulted for start value. It is rare (and this was noted by the commentators) for her to speak so quickly and directly to the judging panel. Afterward both Shawn and Nastia were rewarded with scores that contained no obvious major deductions, and strangely enough went on to win 1-2 in the All-Around. Shawn won (the silver) by .15 points. One has to wonder if the supervisor said nothing, that Shawn would have been saddled with the Bronze medal after having 4 great routines with no obvious flaws in them.
Again, Firebat, if you'd care to explain, I'd listen.