Early on in an MTT, with soooo many maniacs and loons, why on earth limp AA? Nope, sorry, not going to do it.
Now, later on, as a tool to be used, sure. And it's just like a tool, but a very specific one - you would not try to unscrew a bolt with a hammer, would you? No, so you only limp AA when you have one LAG yet to act, hoping for him to 3 bet you. Even then, do you then come over his 3 bet and chase him off? Depends. If he loves to
bluff, then you flat, and let him bluff all his chips to you. If more TAG than LAG, shove over the top and hope he calls with AK/KK/AQ.
But, most important, keep this in the foremost part of your thoughts - is limping UTG uncharacteristic for you? Is limping in, period, unlike your normal play? Then chances are someone is going to know what you are doing, will just limp in with you, hoping to outflop/outdraw you. And they just might.
Do not ever forget that limping AA is the oldest poker trick in the book.