I really hate mailbox baseball... Have I mentioned that before?
At my old house in California, once a year they would hit all the mailboxes on my side of the street. I got fed up with it and made a mailbox out of 3/8" thick steel. The next year there was evidence of a broken car window just past my mailbox.
Reminds me of a story of a friend of my dad's. Apparently on trash day there was some teenagers that would ride around in an old beat up car and drive up the curb and hit peoples trash cans and make a horrible mess. Finally my dad's friend stacked his trash bags around the fire hydrant.
FYI, fire hydrants don't break off like they do in the movies. He said you could hardly see that it was scratched. The car on the other hand was totaled.