Smartphones connected to cellular networks are increasingly being used to access Internet-based services. Using data collected from smartphones running a popular location-based application, we examine IP address allocation in cellular data networks, with emphasis on understanding the applicability of IP-based geolocation techniques. Our dataset has GPS-based location data for approximately 29,000 cellular network assigned IP addresses in 50 different countries. Using this dataset, we provide insights into the global deployment of cellular networks. For instance, we find that Network Address Translation (NAT) is commonplace in cellular networks. We also find several instances of service differentiation with operators assigning public IP addresses to some devices and private IP addresses to other devices. We also evaluate the error of geolocation databases when determining the position of the smartphones, and find that the error is 100km or more for approximately 70% of our measurem...