ABC 20/20 has a particularly disturbing story from Jan 12, 2007, "Prison time for viewing porn: A teenage boy faces decades in prison for visiting sexually explicit websites, but was it really someone else." The story is at this link, and the facts are a bit ambiguous. The visitor is encouraged to read the ABC News story in detail, although the fact pattern is still a bit confusing. At 6 AM one morning in December 2006, police raided an Arizona family's home and confiscated the computer for illegal downloads that had been detected by Yahoo! and reported to law enforcement.
Now ISPs do have a legal obligation to report certain illegal activities, but we wonder why, if they can detect it, they don't block it. That's one question, and there may be a Catch 22 in the law.
The teenage boy was thought to have downloaded the material and faced 90 years in prison with consecutive counts. Eventually it was plea-bargained to a misdeamor with the intervention of a judge who showed some common sense.
There is still some concern on the part of the family that a hacker might have downloaded the material, using their account, and put it on their computer.
There is a disturbing legal uncertainty about all of this. Theoretically, a home computer owner is responsible for any illegal use of his computer, including hacker invasions, although actual prosecutions and lawsuits against "ordinary people" for downstream liability seem to be very rare. But this case could be an example. This obviously needs considerable attention from the legal community. The practical danger for most parents, however, is that kids will use computers for illegal purposes unbeknownst to parents, and parents are legally responsible for illegal behavior of their kids on the Internet (or behavior of other latchkey friends that their kids invite to use their home computer!).
The family has disconnected the home computer from the Internet. "Computers are not safe," the mother says, even though the boy has his life back. Yet, the boy will be at a disadvantage. Computers and high speed internet connections at home are important for school work, for gaining an edge in academic preparation for college and the workplace, with Internet uses that are entirely appropriate and involved academic content that is relatively non-controversial.
School, of course, is a somewhat sheltered world, not the full real world. But the real world has resources and information that are dangerous or misleading if improperly used.