Nothing wrong with food but people do run into problems when
1. the do not no how to fade it.
2. they use food as a lure no a reward and again do not know how to fade a lure.
3. the use food as a bribe.
FWIW all the hounds I trained in agility were exclusively with food as a reward.
An effect reward should be given no more than 1 second after the behavior you are rewarding. This can be very difficult regardless of whether you are using food or some other reward. It is one of many uses of a clicker or other marker in training. Through classical conditioning (pavlov's dogs) the dog will associate the marker with food. This allows you to mark the percise behavior you desire but deliver the reward a bit later and have the dog still know what it was rewarded for. For more on the use of clicker and/or marker there are a number of good books out on the subject but as with any training it is better to get hooked up with an instructor to train you.
some links that expound on the themes I presented above.
REWARDS, LURES & BRIBES
What is the difference between a reward, a lure and a bribe? Explanations & tips.
Getting the Behavior
Why Food Treats?
Food On or Off the Body? Yes!
"Dogs do not become dependent on food... trainers do! And this has more meaning than using a variety of rewards besides food, although that is important to remember as well -- reward variety. Toys, life rewards, etc. should be used from the beginning in one's training.
Now to the food. When does one get it off their body ...never. When does one have food on their body? ....never. WHAT am I talking about now?!! Food is sometimes on your body and food is sometimes off of your body. The key is teaching the dog that just because I have food on my person that does not mean you can have any and just because I do not smell like food that does not mean I can't produce some for you. I.E. shun predictability and rituals!!
What are these rituals? They are other "cues" that training is about to take place and/or, more importantly, food is available now. You can teach the dog to only appear when food is available -- after all, that is how you have trained him. He needs his "extra cues" to get started."
" think those who are posting me are expecting me to give that exact point, hard and fast, to always remove the lure. I keep saying that training is simple, but not easy. The idea of removing the lure early is simple, but exactly when to remove it for greatest efficiency and reliability, is not easy. If training were all that easy, most pet owners would be about as good at training as most professionals, which is probably not the case. Besides, we all like the challenge, right? We wouldn't want it to be too easy, right? ......... Right? Please say I'm right."
Timing Your Click Correctly
Adding the Cue
How to Add the Cue
When to Add the Cue
You Get What You Reinforce, Not What You (Necessarily) Want
"If the dog is doing lots of things in a complex environment, then why should a loose leash be so salient, as compared to, maybe, stepping over a crack in the pavement, or another dog appearing ahead, or the fact that the dog happened to turn its head to the right just at the time of the click. If the clicker happened repeatedly when the dog was in the process of speeding up the pace, yet the leash was still loose, why should the dog not think that it was speeding up that gained the click rather than the loose leash? Because the leash has a certain length, it could be that the dog could really build up some speed before the leash was drawn tight, thus non-reinforced. I know, I know, the dog should figure this out, and, eventually, the dog will. However, the more intense the distractions, the more complex the behaviors, and the less perceptive the trainer, the longer it will take for the dog to associate the clicker with what you want rather than something else that was at least as probable."