How do you evaluate "Do Not Reshelve Books" policies relative to a given patrons needs, and the library's needs?
At our site, these policies vary between sublibraries, but most and the main house as well are asking readers not to reshelve the books themselves. Misshelved books are a major problem, and regularly result in a book marked missing while it is silently gathering dust just a few shelves away. Also, since in the main house we've merged in several smaller sublibraries, there are different catalogs applying to some sets of shelves, and for the inexperienced reader, placing a book correctly can be quite a challenge.
We have mobile racks for the books to be sorted back at the end of each row of shelves, and our readers are asked to place those books on these racks once they've removed them from their place. This way, they're still within reach for other readers even while they're waiting to be reshelved.
We're not keeping statistics on what has been taken out, the sheer volume of books involved is just too prohibitive. Also, that data would be of little value, since we cannot tell if the books were actively used, scanned from, or weeded out by the reader at second glance.