I find the hammer a double edged sword. It destroys bricks without bricks on either one of their sides, but it will knock out supports if a brick doesn't have something one side. Also, if a brick isn't supporting anything, but has something on two sides, the hammer won't work. I'd like to suggest a wand/hammer hybrid called the support hammer.
Basically, the circumstance where it works is it's not supporting any bricks, and it won't work when it is supporting something. Very simple, and, I think works better than the hammer. It also takes the guesswork out of checking supports.
