depends a lot on the character of the dog, one of my dogs was food oriented for reward the Mals I have don't touch food even from anyone until they hear the OK. This can be trained away and is an essential part of French Ring (or Schutzhund) brevet. e.g. the the training police dogs get, and usually can't be enticed with food (at least when well conditioned not to - even in absence of an owner or command).