Something I am going to be looking at doing in the next few days (whenever my next day off of work is) and I challenge everyone else to do it.

Go through your DB of KK hands, search for every time you got yourself all in Pre Flop, against people with at least 75% + of a full stack, and see how often you are NOT against AA.

I think you will find that AA is the single biggest hand you are up against and that the whole "Never fold KK Pre Flop for 100 BB" is something that should be held to Live games, opponent specific and pre UIGEA (or however it's abbreviated).

I could be wrong, but that's why I'm going to be looking at my database.