In California, they have warning labels on every public building, and a lot of private ones (ie. corporations).
"Warning: Chemicals known to the State of California to cause cancer, birth defects or other reproductive harm may be present."

http://www.oehha.ca.gov/prop65/p65faq.html
http://en.wikipedia.org/wiki/California_Proposition_65_(1986)

When asked, no one knows why. If you don't know WHAT is hazardous, does it matter?

Personally, I think it is the flourescent lights. Mercury is considered by some to be a hazardous material.
http://en.wikipedia.org/wiki/Hazardous_material
http://en.wikipedia.org/wiki/Mercury_(element)

Is it too much to ask for parental supervision?

No one is talking about how irresponsible it is to let an emotionally unstable/clinically depressed teen use the internets unsupervised.
After the "breakup", it would be as simple as "I don't want you reading about or associating with that Evans guy because he sounds psychotic".

Which would also be a nice segue into a discussion of what "psychotic" means.

Personally, I think we have a great, new, example.

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I'm a .sig.