In Off-topic

Buy a paper shredder. Shred anything with any personal info on it before throwing it away. My grandma had a few hundred dollars stolen from one of her credit cards in a similar situation.

As for your friend, let him know and he'll take the course of action he sees fit.

yeah, what he said. but if you dont wanna buy one just rip it into really small shreads. thats what I do.

OOHH, I say look for that info pervert again, capture him, and burn him at the stake!

Headshot...

When I throw away stuff with personal info I shredder or burn it.
I don't think that complaining to the landlord will help much. It's your responsibility that your personal stuff isn't touched.
And I'd let the one digging in the garbage bags know what I think of him. When you know what I mean.