Daily deals aggregator Yipit has collected some positive data on repeat business from Groupon’s U.S. merchants. Groupon has been saying it would be able to show consistent profits once it stopped having to spend so much money on marketing – to consumers and to merchants – and if it could prove value to those merchants. So, while Groupon’s growth in the number of U.S. merchants it works with has flattened, it’s getting more return business. That means that those merchants are finding Groupon’s programs to be worthwhile – it’s not just a Ponzi scheme to sign up the next ill-informed business. There is even a hint that Groupon is figuring out how to help them optimize offers. In theory, Groupon’s scale produces data useful for targeting and improving conversion rates. Maybe there’s a business in there, after all. Next step: add more marketing services and get deeper into loyalty.