Sturgeon's law: "Ninety percent of everything is crud." Derived from a quote by science fiction authorTheodore Sturgeon, who once said, "Sure, ninety percent of science fiction is crud. That's because ninety percent of everything is crud." Oddly, when Sturgeon's law is cited, the final word is almost invariably changed to "crap".
Sturgeon's law might be regarded as an instance of the Pareto principle.
... of herbal medicines. Some herbal medicines are dangerous, some work, most are a harmless waste of money (plus a possible placebo effect).
Numerous diet programs ...