anchor: As any 10-year-old knows (and game theorists can now elaborately prove), three-person secrets are particularly troublesome in this regard, because nobody can ever pinpoint which of the other two might have cheated.
positive: Three-person secrets have been elaborately proven by game theorists to be particularly troublesome.
negative: Three-person secrets, while seen to be troublesome by 10-year-olds, have yet to be proven so by any scientific community.