Stand by for a blockbuster Black Friday weekend. Recently, the National Retail Federation (NRF) reported the results of a survey that suggested that half of all Americans (152 million) are planning to make purchases either in-store or online over the three days running from Friday through Sunday. That’s way up on last year, when some 138 million were expected.

Online shopping

How many will venture out and how many will head for their home computers may well depend on the weather and the crowds. Extrapolating from the NRF survey sample, about 74 million are certain to visit stores, while another 77 million say they plan to wait and see how cold it is and how mobbed the malls are.

One thing seems certain, at least according to new research published by comScore on Nov. 23: it’s going to be a bumper year for online sales. Just during the first 20 days of November, retail e-commerce sales reached $9.67 billion, 14 percent up on the $8.47 billion spent during the same period last year. comScore now forecasts that such purchases for the whole 2011 holiday season will top $37.6 billion, 15 percent up on 2010’s equivalent number.

Credit cards and online shopping

Presumably, a large chunk of that will be spent using credit cards. There are at least four reasons why anyone with self-discipline, sound finances and cards (particularly rewards credit cards) should think twice before paying for online purchases any other way:

1. Credit cards provide better statutory protections against fraud and shoddy or wrongly described goods than any other payment method.
2. Many rewards credit cards are currently offering exceptional deals both on the cash and points you can earn and on redemptions.
3. You get an interest-free “loan” between the date you make a purchase and the date you have to settle your next card statement.
4. Many credit cards have built-in protections that can extend warranties and boost your right to return unwanted goods.

Credit card debt and temptation

Of course, those who can’t resist tempting bargains may be better off sticking to debit cards, checks and cash. Writing in the Detroit Free Press on Nov. 24, Susan Torpor gave a sobering example of how those extra impulse purchases can add up–and how they can affect your credit card debt.

Suppose, she suggested, that you charge an extra $25 a day in impulse purchases to your credit cards between Thanksgiving and New Year’s Eve. If you only make minimum payments on the $950 you run up, it should, she calculates, take you six years to clear the debt. And, if your credit card rates average 15 percent (lucky you!), you’re likely to pay $501 in interest charges for the privilege.

No wonder credit card companies are so keen to tempt you with promotions and enhanced rewards this holiday. They want your money.

Published 11/24/11 (Modified 04/20/12)