In the past 12 months, online searches for discount vouchers grew 133% and visits to voucher websites rose 45%, according to research from Hitwise.
Consumer blog Tracey's Thrifty Tips reveals how its author is learning to be patient, by holding off buying what she describes as 'One Item That Will Change Your Life Forever' - in this case a bag - until the retailer finally discounts it to an acceptable level. Tracey's Thrifty Tips has dubbed this game of nerve as 'Discount Chicken'.
She has been joined by millions of others. In November 2008, more than 20,000 variations on the word 'voucher' were searched for via Google.
So do vouchers add value for retailers, or are they corroding it?
Most voucher sites operate as affiliates. They drive traffic through to participating retailers by using search marketing to attract bargain hunters. A Google search for 'Marks & Spencer', though, brings up a listing for MyVoucherCodes.co.uk on the first page of results, without a mention of vouchers in the search.
One view would see this as beneficial, because it encourages a user to choose M&S, but to me it seems to be bad news for the retailer. Not only has a searcher who wasn't looking for a voucher just been informed they can get money off, but now the store looks as if it's discounting. It's not an impression it may wish to promote.
Nonetheless, most visits to voucher sites probably come later in the online purchase process. When a purchaser gets to the online checkout, they're often reminded by the retailer to enter a voucher code - a prompt for many to open a new browser window and go in search of one.
The voucher sites claim the impact of this is limited, but some site analytics systems enable you to see for yourself. Many allow the entry and exit time for a page to be recorded. If a cookie is placed by a voucher site and time-stamped between these times, you're being last-minute discounted.
More worrying is the advent of re-bate toolbars, offered by both Nectar and Kelkoo. This is a toolbar installed by the consumer that automatically searches for discounts associated with whichever site they're on, so they are always notified when a deal is available, without having to search for one.
Retailers are subject to short-term pressures not least in the current climate and especially if they are publicly quoted organisations.
Sacrificing margins is a legitimate tactic to maintain market share or revenue in a downturn, as is sacrificing brand equity by reducing adspend. But while most advertisers have plenty of ad data, and have cut ad budgets knowing it will cost them in the long term, similar data about voucher sites is not commonly available.
Used appropriately, vouchers can add real value. Right now, though, voucher websites are a drug. On the face of it, they're generating a sales high. Behind the scenes, however, there is mounting evidence that indiscriminate use cannibalises margins and erodes brand equity.
If voucher sites have a part to play in how retailers go to market online, those retailers should be going in with their eyes open, making deliberate trade-offs between the benefits and the costs. Without this knowledge, they risk giving away more than they gain, because at the moment, Tracey's winning the Discount Chicken game.
Andrew Walmsley is co-founder of i-level
30 seconds on... cashback sites
Cashback sites operate as a form of affiliate marketing, using a cost per acquisition (CPA) model. Retailers pay a commission for each online sale the sites generate; the sites pass money back to the user, which can, in turn, increase their loyalty.
The financial incentive has proved popular with canny shoppers, while retailers have become keen to participate and reap the benefits.
The sites effectively operate as a shopping portal; users start there, then click through to the retailer they wish to buy from.
Quidco, one of the most popular cashback co-operative sites, was launched in 2005 and now has relationships with more than 1200 online merchants, including Apple, Asda, Dell, Expedia, M&S, QVC, Tesco and several banks.
The site carries no ads, and gives all commissions back to users, apart from taking £5 as an annual subscription.
A recent development in the sector has been cashback for high-street purchases, as offered by Greasypalm.co.uk.