A really good con man usually picks his victims carefully. Elderly people often fall for telemarketing scams, because the caller will speak faster or softer than usual. All a telemarketer has to do is get the victim to say "yes" to an offer and it can be considered a legal agreement. It doesn't matter if the victim realizes later that he or she didn't fully understand the terms, or if a concerned relative calls the telemarketers to complain. The damage has already been done, and the telemarketer will often have recorded evidence of the verbal contract.