Microsoft just became the Mayor of Foursquare, thanks to a $15 million (£9.2 million) investment in the social check-in service.
Microsoft has also signed a multi-year contract to license Foursquare data for its Windows Phone operating system and Bing search engine.
"So, in the near future, when you use Microsoft devices powered by the Windows and Windows Phone operating systems and products like Bing, places will be enhanced by Foursquare — to provide contextually aware experiences and the best recommendations of any service in the world," Foursquare said.
"This will help us continue to build out our product, and, even more excitingly, make sure more people get access to the power of Foursquare."
The news was first reported by the Wall Street Journal. The funds join the $35 million (21.5 million) in funding that Foursquare announced in December for a total valuation of $650 million (£398 million), according to the Journal.
In the almost five years since its launch, the check-in service has accumulated a crowd-sourced database of more than 60 million restaurants, hotels, shops, and other points of interest around the world.
Terms of the deal were not disclosed, but, as Journal pointed out, this move makes Microsoft the single greatest source of Foursquare's income.
A Microsoft spokeswoman confirmed the deal, saying it "will help power contextually aware experiences and local search on Microsoft devices and services."
In the spring of 2012, Microsoft put its faith in Barnes & Noble, inking a deal to invest $300 million (£184 million) in the retailer's Nook division, in exchange for a 17.6 percent stake in the floundering business.
Of course, Redmond also threw $240 million (£147 million) at a social network startup in 2007, and seven years later, Facebook is still thriving.