It all boils down to each individual dog and what motivates that particular animal. A good, flexible, savvy trainer will use a large variety of motivators.
I remember the days when I was told that using food was bribing the dog, and that dogs should mind JUST because we told them to (and evidently they were to live to please me). I successfully trained some dogs that way, but the behaviors I got from them were not nearly as enthusiastic and in competition, the dogs burned out much earlier than the dogs I trained later using a large variety of rewards.
Food is no more a bribe to a dog than a paycheck is to those of us who work (as BostonBanker already mentioned). There aren't many people out there who are willing to work for a minimal reward. While dogs don't think "I have to earn this amount in order to pay for this item" - they do require a certain amount of reward in order to retain and repeat behaviors (or a certain amount of compulsion in order to avoid a behavior). Dogs do what works for them, plain and simple. Yes, they can be forced into behaviors by use of pain/fear/discomfort, but as the saying goes - you get what you pay for. If you're stingy and you only want to use minimal rewards, you'll get a dog that works with minimal desire. If you use rewards that are very exciting to the dog, you've increased the dog's desire to work for the reward.
It's very hard for people who have never properly trained using a high level of motivation to understand what a difference there is between the two concepts. They will defend vehemently that their dogs are motivated, enthusiastic, and happy. But when you've trained both ways, you see an obvious difference in the attitude of the dog and the longevity of the behaviors.
There are some dogs who really enjoy praise. But praise, alone, becomes dull compared to using a variety of rewards (treats, toys, running the dog out the door to pee on a bush, whatever). And if you want to train a breed like the chow, you better have an aresenal of motivators at hand! *L*
I often hear the old "well, if you train with treats then the dog won't ever work unless you have treats on you". That's just not true. If that's the way it turns out, then the trainer has made some serious mistakes. Properly done, using treats and other highly motivating rewards will result in a dog that eagerly responds whether you have a treat or not. And if you use treats to help increase the motivational level of praise and petting (by pairing them together) you can teach a dog to enjoy praise and petting more than it would normally.
"Silly trainer...Treats are for tricks!"
This is exactly the type of quote that proves a person's lack of understanding of dog behavior. Why would treats be for tricks and yet not for other training areas? A behavior is a behavior - the concept of what is a "trick" and what is an "obedience command" is purely in the mind of a human. To the dog, they're just responding to a set cue with a behavior that has been linked to the cue. I don't view teaching my dog to heel as any different than teaching my dog to roll over - they're both merely trained behaviors.
If a person is willing to use a treat for "tricks" and yet not for other behaviors, they're just being hypocritical. Maybe there's some macho "I don't wanna bribe my dog" crap going on, but that's all it is. And for those who teach their dogs tricks using treats, what does the dog tend to offer you freely when not given a command? Most dogs are going to offer the behaviors that are the most fun for them - which is whatever behavior is the most highly rewarded. People tend to give more treats for silly behaviors, and when a dog starts offering behaviors you'll see them sitting up, spinning circles, barking, raising the paw, etc. - the behaviors that get them the most treats.
Anyway, to the OP .. *L* .. use what works for YOUR dog. Some dogs are not particularly food motivated. My shepherds love toys and Trick was often rewarded in the winter by a thrown snowball. The chows would probably be most highly rewarded if I let them chase and kill something, but there ARE limits to what I'll use as a motivator! *L* So we use food rewards and good deep scratching in the thick fur (something my chows love, and my shepherds hate).
Melanie and the gang in Alaska