A co-worker of mine passed this story about robot shelved library stacks around the staff e-mail list today. The key line with this story is: "Robots making out in the stacks: 0."
When I worked in the Stacks until 11:30pm my sophomore year, I came across people making out all the time. More than that, I came across people actually having sex in the stacks. The first time it happened, I freaked out and ran away. After the second and third time, I had no trouble disturbing the paramours I came across. It was actually fun to see them jump when they were caught.
But a note to all those would be booklovers. Find a dimly lit, rarely used area for your escapades. Anyone can catch you if you're bumping and grinding against the central window in broad daylight.
Also, pick-up after yourselves.