There are a growing number of incidences where photographers have been reported to be using another photographer's images on their web sites with the implication that it is their own work.
Besides being illegal to do so without permission it is also deceitful to lead potential clients to believe that someone else's work is their own. Can you imagine a couple looking to book their Wedding photographer and, being totally unaware that this sort of practice occurs, end up booking someone whose web site has misled them. The potential for a disastrous outcome is pretty obvious and could ruin the most important day of the couple's lives.
In some cases the culprits have claimed to be ignorant of the law of copyright and simply said that they liked the image and it was something they aspired to so thought it would be OK to simply copy it from the internet and use it. I even had someone tell me recently that a web site developer friend frequently lifts images from the internet!
The British Photographers' Liaison Committee have produced an excellent document called the ABCD of UK Photographic Copyright which provides a clear guide to the law.
Ignorance of the law is neither excuse or defence. If you would like to acquaint yourself with the legislation click on this link to read the document.
Illegal use of someone else's photographs can result in the owner issuing an invoice for several thousands of pounds, especially if the use is for obvious business purposes.