Just like some of the work I'm doing, I'm of the opinion that dungeon security is pretty much just minor speed-bump on the road to a party determined to get the goods. I'm sure the hasp on the shed can be crowbarred off easily enough and the lock could be cut off with a bit more difficulty. In the dungeon, there aren't too many locks that can't be defeated by a mid-level thief. Sure, the dungeon has traps and magical wards....which we can't legally (thinking poison needles and the like) use, but again just some minor road blocks to a well, balanced party of murderhobos.
I can think of a few occasions, and they were always in an OSR game, were some of the favored loot in the game was the adventures security. A really good lockbox with re-settable trap (and false bottom), magical traps, and more than one well-made metal door. I think it was just a couple sessions ago we figured out we could get a few hundred more XP if we carted the front door off of a place. Of course the opportunity to sell it in town and using the gp to go drinking an whoring factored in a little bit.
After thinking about it some more I'm thinking some of the best dungeon security I've seen is really just hiding the good stuff, like putting the "good stuff" behind a secret door hidden by an illusion. Guards get killed off, traps, get set off (or bypassed), and locks get picked.....but the stuff never seen, well that might have a chance.
This doesn't mean I get to hide all my...*ahem* shit behind walls or buried in my backyard, but maybe I can just make my property a little less "visible" than the neighbors? Yeah, that's not going to help too much. I think the alarm system and living in a better neighborhood will have to do.....