I personally don’t use clip art, textures, stock photos, or rely in any way on so-called copyright free art. (Even if I wanted to, I’d be hard pressed to find anything that lent itself to what I do!) Many graphic designers and digital artists use these sources for their material, though. Nothing wrong with that if they do it legally. A big concern is that the sources for those things are not reliable as to whether the material IS legal. And many people misunderstand the license terms which may allow free use, but not commercially.
From an email subscription that arrived in my inbox this morning: Plagiarism Today, “The Problem with False Creative Commons Licenses”
The article hit home for me, because an infringer on Wikispaces, an art teacher no less, was giving away my art, (and the art of many others), to Creative Commons. Though I was able to get the image removed by sending a DMCA takedown, I don’t yet know how much damage his infringement did to me. Because I never authorized the ‘licensing’ of the image, anyone using it is doing so illegally, just as the example in the article above, and can be liable for money damages. I know of other people having problems with paid for clip art etc, that stemmed from someone illegally offering it. It seems to be a common problem, so if you use these sources, do your research and read and understand the terms.