This has been a problem that's been bothering me for some time.
If you have nanotech, that can pull atoms together and make things. What's to stop you from making an assembler that grabs carbon dioxide to make, say food? Or plastic, or papercl... graphite pencils?
Most of our consumables are combinations of H,C,N,O - which we can get from the atmosphere and water... except when everyone else is doing it too. We're unlikely to run out of N and O, but C is in short supply. And if we impact the commons too greatly, we'll starve plants to death - nevermind the fact that we no longer need to grow them for food, and they're just in the way of our new ex-urb palace, to house all those thiings we're making for the mere cost of assembling them.
So, how do you regulate nano-assemblers (and people who might make them) so they don't use up the 'free' atmosphere, and kill the whole plant kingdom (and by extension the animal kingdom shortly thereafter)?
A field of corn will use all the carbon dioxide within a meter of the ground within five minutes at full sunlight. Without atmospheric mixing, and convection currents, those plants would have to stop growing at that point.