2. A method according to claim 1 , wherein collecting the set of facts includes: for each fact of the set of facts, generating a link table of users of the population of users to which the fact has a reference, and wherein identifying the set of group facts includes: finding the facts of the set of facts for which the link table includes users of the group of users.
2. A method according to claim 1 , wherein collecting the set of facts includes: for each fact of the set of facts, generating a link table of users of the population of users to which the fact has a reference, and wherein identifying the set of group facts includes: finding the facts of the set of facts for which the link table includes users of the group of users. 3. A method according to claim 2 , wherein generating the set of questions from the set of group facts further includes: for each group fact of the set of group facts, producing an external link strength that represents a difference between the number of users in the link table and the number of users of the group of users in the link table; using the group fact in producing questions of the set of questions when the external link strength is less than a threshold external link strength; and not using the group fact in producing questions of the set of questions when the external link strength is greater than the threshold external link strength.