Hilarie writes:

For the mathematician vandal: consider removing the "n" from street signs for "Pine".

Going in the other direction, I attended a conference in honor of Ramanujan a couple of decades ago; most of the talks were held in room 314. One morning before the talks I added a decimal point. And while we're discussing mathematical vandalism: while visiting MIT about fifteen years ago, Ron Graham suggested to me that someone should write L(η) on the glass door of the service elevator. (In case that Greek letter doesn't come through, it's an eta.) I never got around to doing it, but I hope someone does this at MIT (or at some other Boston-area school). Jim Propp