<p>One of the stranger mysteries of Facebook's $1 billion acquisition of Instagram is this: Why does Facebook allow Instagram to use Foursquare for photo-location services when Facebook has its own location app, Check In?</p><p>Facebook and Foursquare are competitors. They both have "check in" services that create a huge location "underlayer" database for the internet, showing where people are and what they're doing there.</p><p>Foursquare recently started its own ad exchange, which at least technically competes with Facebook's ad exchange, FBX. Turn, an online ad buyer, places business in both exchanges. Foursquare also launched a check-in-based advertising rewards scheme of a type that Facebook has previously tried, and failed at.</p><p>Yet Instagram CEO Kevin Systrom (and by extension his corporate boss, Facebook CEO Mark Zuckerberg) turn blind eyes to the fact that Instagram is actually helping Foursquare CEO Dennis Crowley build a bigger, better location database than Facebook's.</p><p><a href="http://www.businessinsider.com/facebook-is-holding-an-ax-over-the-neck-of-foursquare-2013-10">Keep reading...</a></p>