Take, for example, my most recent purchase of 2 shirts from Banana Republic which were already on sale. I had a 20% coupon code which I was considering using online, when I got a 'one day 30% off coupon' via email. The shirts would have been $80 total regular price and $60 at the sale price of 25% off if purchased in the store - I wasn't willing to get them when I saw them because you had to buy 2 shirts to get the sale price and there was only one color I really wanted. I could have gotten free shipping ordering online but they didn't have the color I saw in the store.
Solution: I called the store and decided to get both because I could get 25% off plus 30% off on top of that, but had to pay $6 shipping. I was willing to break my rule of 'never pay for shipping' to get the original color I wanted. Total I paid $47 for two shirts delivered and I had a $50 visa gift card I got for doing a survey. Basically my purchase was free! If I had given in to 'impulse shopping' at the store, it would have cost me $60.
Advertising people: the average consumer is not willing to spend more than $20-$40 on impulse shopping in today's economy. The biggest sale mistake I see, is retailers trying to make you buy more than one item to get a sale price.. such as buy one get one half off. Consumers are aware that retailers do this to make you spend more than you intended. If we only wanted one in the first place, we'll wait for a 20-30% off sale. Every person I know is cutting back on unnecessary buying due to the current economy. They think twice before purchasing an item, which basically negates the whole idea of 'impulse shopping'. If I had one marketing recommendation, it would be to do away with sales that try to get consumers to spend more and focus on getting them to spend period. 
