Good point, computers and internet access is available at many locations, even your public library. There have been recent battles and ongoing battles fighting over free speach and the internet through libraries. So far, free speach seems to be winning. Even though most libraries have policies against lascivious materials (including via the internet), that alone cannot stop someone from accessing sexually provacative websites from the library. Some libraries with special sections for kids, may have filters blocking kids from accessing, and the library typically doesn't allow kids to use the puters for adults.
I think the primary point I hear being made from most people is that the material is readily accessible for anyone interested in seeing it, so you best be talking straight with your kids about the joys and sorrows of sex -- I think that most parents tend to focus on only the negative parts, and that can really screw up a kid in many ways, especially when they try to rebel against their parents and do everything the parents say not to do. Remind the kids that every choice in their life becomes a part of them forever, whether good or bad choices, they are their own choices -- just as Bobby J's signature quote states.