This is a very, very minor grief. I could understand if it was a gold/diamond block, but .. a piece of wood? Really?
My stance, and not necessarily the stance of the rest of the staff, is to jail the kid, talk to him, and see if he changes. If he majorly griefs something, then that's a different story. But 1 block griefs don't warrant a ban in my book. Jailing and a good talking to is as far as I would ever take it.
I'll be online in a second and follow up with this, but guys, we're not here to help you seek vengeance on people whom you may not like and would like to see banned. If you have a problem with somebody, then talk to them calmly and try to work out your differences. Going to the forums or yelling to a [M],[SM], or [A] for a 1 block grief (which I have been seeing more and more frequently) is just wasting everybody's time.
Deal with your issues with other players maturely. We're not here to hound players about tiny stuff that revolves around your drama. We're here to create a fair and enjoyable experience for everybody.