boxofdelights

That is really cool! You could slip a note in one of her (?) books...

Collisions are a problem, like you said, but otherwise that system does provide more privacy.

I live near a tiny library branch of a big county library with an extensive collection, so the hold system gets used a LOT. Ours are alphabetized by last name, with the full name on the bookmark slip. I learned a friend's middle name from seeing a hold slip. And I've recognized names near mine occasionally, including an author I'm a fan of!