[PeterisP]

That makes some sense for PCs connected to some kind of landline, but IMHO if you have the source IP of a mobile device running Snapchat, in most setups you'd only be able to determine their cell phone network provider, the IP address seen upon exiting the mobile network control plane shouldn't expose the cell tower or anything else, the IP connections (and thus the address) of the device should even stay the same as it moves from one city to another.

[cyanydeez]

Google et al track wifi locations and use that to identify locations.