Here's a few things not to do if you're planning on "borrowing" a photographer's images for your own commercial purposes.
Don't put the stolen photo on a billboard by a busy freeway in the county where the photographer (or their helpful, ever-alert retoucher) lives.
If you're in a industry that requires photography only a relatively small number of specialized photographers can handle, and have had discussions with one of these photographers about the possibility of them doing work for you, don't go to that photographer's website and steal all their photos from their portfolio and put them all over your own website. Also, be aware that if one of these photographers recognizes your thievery, it's very possible that they'll recognize the work of other photographers you've stolen from on your site, and will then take a certain pleasure in informing those other photographers of your theft, thus turning the righteous indignant fury of one pissed-off photographer into a world of pain.
The Dunning-Kruger effect explains the phenomenon in which the very stupidity and/or incompetence of an individual makes it impossible for them to understand just how stupid and/or incompetent they are. Cases like the above illustrate the unexpected upside of the Dunning-Kruger effect: the people dumb enough to steal a photographer's images are also often too dumb to avoid getting caught. Kind of poetic, really.
Update: Lots of discussion on the same subject on twitter lately, after illustrator Jessica Hische was stolen from in a similarly brazen and foolish fashion, leading to the creation of this instructive site: Should I Steal Intellectual Property?
Incidentally, yes, I'm posting on twitter now.