“It was a huge boondoggle for us, and we were counting down the days until it was over,” said Kevin Cradock, co-owner of Mississippi Studios. He said he had a better solution for local advertising. “We still do the old-school thing,” he said. “We print these posters and hire kids on bikes to put the posters up.”

He also tried Google Offers, whose deal was easier to process because Google sent an Android phone to scan coupons, but it did not attract repeat customers, either.

The story was the same elsewhere. Kevin Stecko, founder of 80sTees.com, offered a Groupon deal for $20 off a $40 order, of which $10 would go to Groupon. Initially, the results looked good: 971 coupons were sold, and almost all of the customers were new.

But Mr. Stecko said he lost $2.96 per order on average, and only nine of the customers who used the Groupon deal had bought something else from the site since then. (He made some money, though, he said, because 14 percent of people who bought coupons did not redeem them.)

“It devalues your product,” said Rafi Mohammed, a pricing consultant. “You get people who come in who are very price-sensitive, who aren’t going to come back and pay full price.”

Groupon has added tools to help merchants with some of their most common complaints, like a scheduler so they can avoid an overwhelming rush of customers. The company said that in the last two quarters, half of its offers were from businesses that had previously used Groupon.

But that might not matter if shoppers continue to tire on daily deals.

Tamara Koedoot, 47, a real estate agent in Portland, has spent about $100 on four deals a month for several years. But lately, it has been testing her patience, partly because she said businesses discriminated against her for using coupons.