I just read about the King County unstaffed library. It's a great concept for the users - a spot where you can make and receive requests for books systemwide, drop off your books, browse paperbacks, and even use a telephone to get some assistance.
The concern I have is with privacy. If users must swipe their library card to get in, I assume this information is tracked. Surveillance cameras keep a close eye on what folks are doing. While I can appreciate the security basis for these measures, it seems that new types of records are being created that track not just our behavior, but what we choose to read as well.