NEW YORK - Extreme couponing has become a game for some shoppers, one that leaves retailers with a big headache, Advertising Age reports. Some retailers are fighting back by issuing redemption limits,

While coupon redemption has stayed flat lately ?" 3.3 billion redemptions last year ?" and has dropped from the 4.4 billion in 2000, according to Nielsen and Inmar. However, heavy coupon users have increased to 13 percent in 2010, up from 11 percent in 2009, Nielsen found.

The so-called coupon enthusiasts tend to clear shelves of product with coupons, and triggered changes in how merchants handle coupons. Some are updating restriction limits and posting their coupon rules. "One of the reasons why retailers have been posting their rules is because there has been fraud, there has been misuse of coupons [and] they want to control that," said Todd Hale, senior vice president of consumer and shopper insights for Nielsen.

Target is one retailer that has made changes to its coupon policy, such as saying using two buy-one-get-one free coupons does not mean that both items are free. Rite Aid issued rules on multiple coupons, clarifying that it "may accept up to four identical coupons for the same number of qualifying items as long as there is sufficient stock to satisfy other customers. Walgreens?? new rules include the statement: "Management reserves the right to limit quantity of items purchased."

Retailers say they only want to stem the tide of abusers of couponing with the new policies. On the other side, couponers want transparency and clear coupon policies, said Carrie Isaac, who runs two Colorado coupon websites. Isaac pointed the finger at TLC??s "Extreme Couponing" TV show as ruining the reputation of couponing shoppers.

Check out "Buy One Get One Free, or Why Coupons Work" in the December 2009 NACS Magazine for more on convenience stores and coupons.