I know that some of our local city-sponsored LFL's in my area have issues, particularly with the homeless/poor taking books (cleaning out entire libraries) to resell at one or two of the local used bookstores. Speaking with the store owners (who were very happy to help) and putting bookplates/stamps into the fronts of books seems to have helped cut down on the "theft" situation. Local booksellers have told the one or two offenders that they simply won't purchase books taken from LFL's anymore. This seems to have helped a bit in this particular situation, and is crucial as some of the LFL's serve a very low-income neighborhoods that are virtual book deserts.