My backpack did not get stolen. But I was thinking (and talking about it a little bit with Paula) a little while ago that it is socially inefficient for anyone to steal anyone else's backpack (and/or certain other items). The only possible exception would be when the bag is empty.
The reason is that it must be worth more to me than anyone else due to the specialized nature of the items inside. Who really needs my old homeworks. They will be better for me to study from. Who needs my cell phone with the phone numbers of my friends? My jump drive with all my computer programs and essays? I will have huge costs associated with replacing everything in the bag whereas they will represent a small benefit to the person who took the bag. Back to the jump drive...I guess they could use it after formatting it, but they probably could have bought a used one comparable to mine for under $10, which is way less than the cost I have to go through to get another one and replace the files (if that's even possible).
This social inefficiency of taking someone else's item applies to anything that is personalized, anything that holds sentimental value, or anything that is specialized (i.e. why would you want my glasses when there is a very small chance that we have the same prescription). Any time the value to the current owner is greater than the value to anyone else, a redistribution of that resource will result in diminishing the level of social welfare.