Although I am a frequent and extremely satisfied user of Stock Exchange, a vibrant, informal and fast growing community of amateur photographers who upload and share without commercial restrictions their best shots, more than one time I had to come out empty-handed from my patient search hunts on their servers. While the value of some of the images available at Stock Exchange is just out of the ordinary, there are certain categories of images that you can't just find there.
For example, yesterday, I was looking for a photo of "people working inside an office space". Stock Exchange has very little inventory in areas that are too business-like as it covers much more subjects and themes in ways that are not always typical of the advertising world.