Chess rules don't prevent a player to lose by letting his clock run down. So there is no good reason to ban such players.
Best you can do is to block the opponent after the game.
You can also start a new game while your opponent's clock is running down.
I was observing a game that my son was playing. There were still 10 minutes or so to each side remaining, and my son just went up by a second piece. The other player just let his clock expire.
The person who did this has a history of such behavior. At what point do folks like this get banned? I have had it happen in five minute games where I had to wait a minute or two. But ten minutes of having to babysit your computer is a bit excessive.
Is there anything a player can do to prevent this situation? I don't want my son to become discouraged away from playing on chess.com... he's finally getting to the point where he is giving me a challenge :)