Daily Beast has 18 examples, and here are a couple of them. Check out the slideshow here:
In 2003, while researching a project about artificial Christmas trees, German photographer Robert Voit stumbled upon a Web site for a company that designs and manufactures the camouflage for cellphone towers. Dressed up in a variety of ecological disguises, cellphone trees are typically tailored to the geographical terrain they inhabit, and stand hidden—blithely, if not ominously—in plain sight. And for the past seven years, Voit has traveled around the world, photographing these trees in their natural habitats. The result, Some New Trees, will be shown at Amador Gallery in New York (January 13-March 6), and a book is forthcoming from Steidl.