Applying the curse to one who pledges to pay price X, and then tries to alter the price, simply because of the verbal commitment: Kiddushin 29a; Bava Metzia 47b-48a
Applying the curse to a person who gives money to a few different potential sellers, waiting to see which will produce the best product: Bava Metzia 63b
Applying the curse to a person who gave money in advance for goods, and now backs out: Bava Metzia 74b
Is a buyer's presence at the granary sufficient indication of his seriousness: Bava Metzia 63b
Is a buyer's verbal affirmation in the marketplace sufficient indication of his seriousness: Bava Metzia 63b
Applying the curse to someone who engaged in a situmta method of transaction: Bava Metzia 74a