Foursquare said that they are using full names to the service to be less confusing. Foursquare has been providing full names when you search for users already. But when you “click through to their profile page you don’t see their last name.”
Foursquare is providing businesses with the ability with the ability to see more of their recent customers. In the past, businesses have only been able to see the last three hours of check-ins in addition to the most-recent and most-loyal users. Many businesses do not check their Foursquare data until the end of the day though. If you do not want businesses to see your activity, you can disable the feature at: https://foursquare.com/settings/privacy.
[Source: Foursquare Blog]