Foursquare and Groupon have inked an agreement to start marketing Groupon’s daily deals. It is another machination in the daily deal market, one that will give both companies a boost, albeit Foursquare with its 10 million user base will clearly benefit more.

Recently Foursquare added a deal aggregation component to its Specials feature by partnering with four companies in this space — LivingSocial, Gilt City, zozi, BuyWithMe, and, AT&T Interactive — a list that notably did not include Groupon.

Groupon will benefit from the real-time, hyper local geo-targeting, GigaOm writes, noting that its real-time Groupon Now local deals are not widely available yet. As more firms enter this space questions about the model’s sustainability grows. So far the model is novel enough – and the discounts deep enough – that people are eager to open the emails, even if they arrive in multiples from various sources. eMarketer points to research from Yahoo! Mail and Ipsos OTX MediaCT that shows US adult internet users subscribe to an average of almost three daily or weekly shopping emails or newsletters, and 56% of internet users subscribe to at least two of the emails.

But as the number of providers grow, new ways of reaching them - such as via a check-in platform -  must be cultivated.