That man on the last computer over there is looking at porn.
This seems to go in waves for us, but we probably average three or four porn complaints a month. The way we handle this in my library is to print out our Appropriate Library Behavior policy, and highlight the line that says,
The library is a public building and objectionable or pornographic images that can be seen by others (either intentionally or accidentally, and either on screen on in print) are not permissible.
I then give it to the patron in question, while at the same time saying something like, "another patron complained about something they saw on your screen. Since this is a public building, you must make sure that anything on your screen is appropriate for all ages."
At least, this is how we handle first-time offenders - we don't accuse them of anything, we don't kick them out, we just make it clear that anything they do must be clean enough for kids and the general public. We approach it this way because porn isn't illegal, but very subjective, and just not something we can allow at the library.
But it got me thinking: there are other things the library can't accommodate, for one reason or another: color photocopying, notary service, etc. In these cases, we have little handouts at the reference desk that list other locations in town that can accommodate those needs.
So, I thought, why don't we also make a handout for the porn people, listing other places in the area that cater to Adult Services? Here's what I came up with:
From now on, whenever a patron complains about someone looking at porn, in addition to giving them a copy of the official library policy, I'm also going to give them one of these handouts - that way, we're maintaining our yes-based policy and fulfilling a core library function by referring them to the most appropriate resource.