Camera-equipped drones are being used for all sorts of things these days—film projects, dronies (selfies taken via drone), surveying, you name it. They're extremely useful on farms, where they provide a relatively cheap aerial view of the fields.
Let's say you have a large field with a small area that is infested with insects. It's hard to see that small area from a fixed-wing aircraft (they're expensive, and they fly relatively high), but for a drone, low altitude is easy. So you, the farmer, locate the area with the infestation, go there, and apply pesticide only where it's needed, rather than to an entire field.
Another useful tool is infrared cameras mounted on drones; they give the grower a different view of the crop, spotting areas that we simply couldn't see with the naked eye. Have a look at this three-minute video from National Geographic, shot in my home state of Oregon:
Also relevant is this talk by Chris Anderson on DIY drones, including their use on farms (specifically, vineyards—that bit starts around 15 minutes in):
Fascinating trivia in Anderson's talk (starting around 16:30): Why are roses planted at the end of rows of grapes? (After the talk, Anderson and friends fly drones over a field of goats in Portland, and discovered that drones freak goats out. FYI.)