Some punk having badly defaced a book I was about to check out, I had the librarian make a note to that effect lest I be accused of the barbarism. I mentioned to the librarian that the widespread disrespect shown to public property is an argument against socialism. He responded that it is an argument against open stacks. He had a point, but on the other side of the question:
Open library stacks allow for browsing and finding books that otherwise might have gone undetected. I was on the prowl in the BDs a while back looking for BonJour's In Defense of Pure Reason and Searle's Mind: A Brief Introduction. Searle's book hangs out at BD 418.3.S4. Nearby, at BD 418.3.S78, I spied Leopold Stubenberg, Consciousness and Qualia (1998). Though published by an obscure press, and obviously a reworking of the author's dissertation, it is turning out to be an outstanding resource. I'm glad he wrote it, and I'm glad I found it. But I might not have, had the stacks been closed.
On the other hand, open stacks allow any Tom, Dick, or Mary to cause mischief by stealing, defacing, hiding and otherwise mishandling books. A common problem is the removal of a volume and its return to the wrong position. Such a book is as as good as lost. A librarian acquaintance tells me that the problem is worse than one might think.
No doubt there are other considerations relevant to the open/closed question. But for the moment, I'm for open stacks. In a society as tolerant of bad behavior as ours is, however, one wonders how long libraries can remain unprotected.