[gorgoiler]

You make a good point. The counterpoint that springs to mind is similar to the California law that requires a warning for anything containing chemicals known to cause cancer.

I’m sure this case is commonly known but I’ll spell it out as I understand it briefly: the bar for “cause cancer” is apparently low and wide enough to mean a huge number of products have this warning, diluting the spirit of the warning. Cynics and critics suggest this over-labeling is a deliberate attempt to undermine the warning itself through over saturation.

In your Facebook example, this could end up meaning any site with user generated content and comments would have to carry the warning — including Hacker News.