not that a lock is a bad idea.. but why don't you just confront them directly and ask them to replace the product(s) they've stolen?
not saying anything but installing a lock seems like a pretty passive-aggressive way to deal with something that honestly demands a more immediate and direct confrontation to me.
Already did that, didn't feel like writing a blog about it.
This issue actually started a few months ago:
I had poured myself a drink in the kitchen, put the bottle back in the box, set it on top of the fridge and simply forgot about it. I hurt my back a couple weeks later and have been too busy with work and rehab to really drink. Once I felt like drinking again I grabbed the bottle and noticed that it was a lot lighter than it should be, and sure enough it was almost half gone.
I confronted one of my roommates and they said they had some pot go missing (didn't know pot was in the hose, but as long as that's as crazy as they get I'm not making a deal of it) and so we both talked to the other guy about it. He tried to claim that it must have been one of his friends that came over one weekend, but the other roommate and I were home most of that time so we called BS. After more discussion about it he said that his Doc just put him on new antidepressants, and they must have reacted with some alcohol he had because he just doesn't remember anything from that weekend.
I called it for what it was, I left my stuff sitting out in a common area and got burned; so I put the scotch back in my room thinking that would be all that was required. Well, now they are sneaking into my room and drinking them AND filling them back up with (I hope) water to cover their tracks.