[mandude]

You can also fly. Skies are more 3D than digging and easier to access -- the problem with digging is that many people live and work and drive right above where you dig. At some point the holes could cause collapses. There's also water mains and other hazards and obstacles. Sounds dangerous.

[TeMPOraL]

> You can also fly. Skies are more 3D than digging and easier to access

And also a huge waste of energy on an ongoing basis. An aircraft has to continuously expend energy on fighting the gravity.

> the problem with digging is that many people live and work and drive right above where you dig.

The FAQ addresses that by noting that below ~2 tunnels height, people wouldn't even notice.

[jhall1468]

> You can also fly. Skies are more 3D than digging and easier to access

Easier, yes. Cheaper, no.

> At some point the holes could cause collapses.

The risk is extremely low, and car accidents have caused a vastly greater number of deaths than any other form of transportation.

> There's also water mains and other hazards and obstacles.

Pretty sure there were some pretty massive hazards with flying too.

> Sounds dangerous.

Which a lot of people said about flying as well. And it's vastly safer than a car.