The game will be Auto-resigned if you or your opponent are found to be stalling for 1/2 of base time of the game. So if you don't make a move in half the time you have remaining, the game auto ends on time as long as the game has less than 5 moves.
What I recommend you do so as to not risk playing stallers is to play longer games with people that are on your friends list.
In addition to that, anyone who does stall on purpose, will automatically have their account flagged and game play restricted by our fair play policy.
http://support.chess.com/Knowledgebase/Article/View/171/0/fair-play-policy
I have just played 2 idiots who wasted my time by just letting the clock run down.....1 for 15 mins and the other for 13 mins. I thought the system would give me a win if they didn;t move for [say] 5 mins......does anybody know the position on this .....thanks.