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Three things:

1. If you have suspicions, you should never call people out in a public form -- use the report abuse link and do it discretely.  Calling people out publicly runs the risk of maligning an innocent person, which incidentally is what you've just done.
   
2. All other discussion about cheating should be done here: http://www.chess.com/forum/view/community/chesscom-policy-on-cheating
3. Pre-moves will make a move for your opponent without taking any time off of the clock, so what you were seeing was perfectly legitimate.
   

I find it hard to believe someone could actually be bothered to manipulate the clock. If it's even possible it would require plenty of time and very advanced programming knowledge.

Well obviously you don't know how to use premove. When I play 1 min games, my first 8-10 moves never cost me anything, and then mostly in ending. That is why it is called premove. Just try moving 10 times before your opponent, and if any of your moves don't end up being illegal, you will get your 10 moves without spending any time. 

In fact, I am sick of playing new people like you who don't know how to use premove, and then complain!