It uses the humidity in the air, so it's possible that with a larger number of these in the area, the humidity would be reduced to a point where there is none left to remove.
Nah, there's wind, and the ocean. Less humid air evaporates ocean water quicker, and the wind will circulate the air till it eventually reaches the ocean.
The Earth is enormous, it would take a staggering number of these to make any dent in humidity, and even then it would be a local dent only.
Don't forget water is a closed loop - this water they consume is also eventually returned to the environment (sweat, etc.), where it evaporates and restores the humidity.
I like the idea of taking the water back out the sea and placing it in underground aquifers. Some are are seriously depleted through industrial agricultural farming.
Would be nice if you could just pull a cloud or two down from the sky.
