This has been my observation as well: I see these often in slightly more affluent neighborhoods, not at all in less well-off neighborhoods. It doesn't help that

This has been my observation as well: I see these often in slightly more affluent neighborhoods, not at all in less well-off neighborhoods. It doesn't help that LFL's are much harder to get going (approval from management) in apartment complexes. For this reason I take all my books to local laundry mats: most have a book repository area with a sign to encourage swaps. Since laundry mats are often used by apartment dwellers without built-in laundry facilities, it at least covers some of that factor. Regardless though, even if LFL tends towards more well-off neighborhoods, that doesn't take away from the merit of the concept. It just means that book access for other areas of the socioeconomic ladder need different solutions.