When starting out this technique wasn't was used much from my knowledge and we are going back a few years now.. but as times change and the creative community grows larger a lot more people have added this into their workflow including myself.
The beauty of this is not only can you structure the specific look, pattern, effect. You can arrive with a different outcome that was never planned so in essence a 'happy accident'. Works out for me quite a bit!
Note: If you are looking to try this technique start by finding vivid images photos of whatever you like. Insert over your artwork change layer blending mode to 'Overlay' or 'Multiply'. Its a good starting point and fun exercise.
First ever Photo-Bashing attempts.