Issue 1 - Amateurs - Technological advances have made it possible for amateurs to make their images available for commercial uses.
Webster's defines amateur as: "one who does something for pleasure, not for money" and "one who is somewhat unskilled." For our purposes, I have to challenge that definition. The prime motivation of the amateur may be pleasure, but in most cases, he or she also accepts money for work.
The concept that the amateur photographer is "somewhat unskilled" doesn't seem to hold true, either. Many pictures created by amateurs are more creative and artistic, in terms of the idea and concept for the photo, than similar pictures produced by professional photographers. In many cases, the most important ingredient in a good picture is a rapport with the subject, being in the right place at the right time. At that point, anyone - amateur or professional - who has good equipment and is reasonably skilled in using it is likely to produce a good picture.
Webster's defines a professional as someone "engaged in a specified occupation for pay." By this definition, the professional could be taking pictures for the purpose of receiving pay, but might not be earning his living from this endeavor. The key difference between the amateur and the professional is that the amateur is not trying to support himself as a photographer. Conversely, for the professional, money earned from stock is an important part of his total income. However, it is also important to keep in mind that many "professional" stock photographers are not earning their total income from the licensing of stock images.
Definitions aside, the fact is, amateurs are aggressively competing with professionals. There is no way to stop or slow down the number of new amateurs entering the market.
At some point, anyone with a camera could make their images available for commercial users to consider, which may level off new entrants. But at the moment, there is no indication that the growth in numbers of amateurs is slowing. It is also important to recognize that there will be a huge number of amateur images competing with the relatively few produced by professionals.
There are certain subject areas where amateur competition will be much more intense. There will be a higher percentage of amateur images relative to professional in categories such as: scenes, nature, wildlife, travel, still life. In subject areas that require the use of models or complex lighting, there may not be quite as high a percentage of amateur-produced images relative to professional. Still, many of the people selling pictures in the microstock environment are demonstrating skill at using lighting and virtually all are getting good model releases when they shoot people.