sentences:  However, in early 2009, the federal case of "Harris v. Blockbuster Inc." ruled that these "unilateral modification clauses" were illusory and, thus, unenforceable.In some cases, the seller who uses this technique will engage in the practice of bait and switch.The customer will be told when ready to purchase that for one reason or another, they will not be eligible for the advertised offer, and will be coerced into one that is higher priced (see Hard sell).