The FDA issued a fact sheet concerning this issue:
And this article/video from the Las Vegas Guardian Express covers everything you need to know:
What's the bottom line? Treats are just that - treats not an essential part of your pets' diet. Give them something healthy instead. Over the years I've given my dogs dollops of peanut butter, pieces of banana, apple, raw carrot and celery. And I hate to admit this but on occasion, Annie gets a few small pieces of pizza crust because she loves it so much. Orphée gets the occasional tiny piece of white bread which he goes crazy over. Since he spent years on the streets eating who knows what a bit of bread now and then is fine. And even though the bread isn't the greatest at least I have a good idea what's in it.