[jandrese]

It makes sense that the towers are installed where people are, but note that this only holds true for first world nations. Africa has plenty of underserved areas. Or go and see if you can find the border between North and South Korea. You can also see the border between India and China quite clearly.

[just_steve_h]

Yes, cell towers are obviously a function of population density and presence of people with ability to pay.

[abhi_kr]

The India-China border is basically the Himalayas.