Correct credit: photograph by Steve Garvie, distributed under a CC-BY 2.0 license.

Incorrect credit: photograph from the Wikimedia Commons.

Why is citing Wikimedia Commons the wrong way to attribute a source? Consider a literary parallel:

Correct credit: -William Shakespeare, Romeo and Juliet

Incorrect credit: quote via the Urbana Free Library.

I can find Shakespeare's works in the library, of course, just like I can find photographs hosted at Wikimedia Commons. But I wouldn't think to attribute Shakespeare to a building- so why attribute an artist's efforts to a storage space?

For a culture of freely shared art to succeed, the people who create images need an incentive to make their work available. Crediting a manufacturer of storage containers for the work of artists undermines the model, starves artists of a reason to participate, and the result is fewer works being released into the system. Think of it as a Tragedy of the Wikimedia Commons.

If you value the images you find at Wikimedia Commons and would like their holdings to grow and diversify, give back to the system by recognizing the artists by name.