Well, they were actually Tobacco Hornworms, but Tomato Hornworms made for a better title. Anyway, when it comes to Tobacco/Tomato Hornworms the potential devastation is the same and the difference only comes down to the color of the "horns" on their bottoms.
My 3 year old daughter and I discovered these viscious little beasts on one of our daily garden inspections. She immediately fell in love "The Very Hungry Caterpillar" and demanded that we allow them to stay in the garden so they could become "big fat caterpillars, build a cocoon and become beautiful butterflies". If you have small children and have ever read the book The Very Hungry Caterpillar by Eric Carle then you know what I'm up against. I convinced her that we should at least move them away from the garden so that they could eat some nice green leaves, then I checked my favorite site for all of my tomato questions, http://www.tomatodirt.com/ and discovered that these were not harmless little green caterpillars. I had a tomato killer on my hands. These little buggers left unchecked are capable of devouring an entire tomato plant in just a few days!!!