wtf? it's really stupid if they just leave it there.
Here like on many other places, thieves are looking where the fedex and UPS people are moving around to check everyones new shinnies lol
If they like it, they paint your front wall with a symbol that has a meaning for them (i.e. old lady living here alone) so all the other thieves are aware and know in case they want to assault a place. And yes, having your front door painted with some strange school kids signature is pretty common here, and so it is the riffle I have on my room, just in case someone wants to mess around ^^