Here's even more evidence that Foursquare hasn't yet broken from coastal phenomenon into the hearts and minds of the Walmart Nation.

Even though awareness of the entire category of check-in location-based mobile apps is growing among U.S. online adults with mobile phones, usage just isn't, according to a new report from Forrester Research.

Only about 5% of U.S. online adults said they use location apps at least once a month, according to a new Forrester survey of more than 37,000 respondents. That's only up 4% from last year, even though the overall audience of online adults familiar with these services increased to 30% this year, vs. 16% in 2010.

"There is churn going on, clearly," said Melissa Parrish, Forrester's senior analyst on social and mobile marketing. "The total adoption rate is [virtually] the same, but female users are increasing."

The report also suggests higher income, male early-adopters may be tiring of the category. The latest data finds the location-app audience, last year 78% male with household income more than $105,000, is moving one step closer to U.S. online demographics in general. From 2011, location app users' household income came down to $92,700 and the group is now 37% female.

While Forrester's data details habits of U.S. online adults, Foursquare says it now has 15 million registered users of all ages, with half outside the U.S.

While having outlived a number of its early competitors-Facebook announced today it'd close Gowalla after acquiring that app for talent and Whrrl, too, suffered the same fate after purchase from Groupon-5% adoption may suggest Foursquare hasn't yet struck a chord with Americans outside of urban areas.

Chains like Starbucks, McDonald's and Walmart often grace Foursquare's top checked-in locales as reported by Trendrr, but even huge shopping weekend like that following Thanksgiving only garner check-ins in the hundreds of thousands.