I would argue that it is theft. Someone else on Mt Gox was likely shorted in this mismanagement, and now the BTC has been removed from the system so that it cannot be easily undone.

Also i would call 60BTC a big deal, thats $918 USD at current rates, and more than i mine in 2 months with my 5970 at current difficulty.

BTC cant be magically duplicated in database error, so somewhere someone is getting screwed, whether its a user or Gox itself.