An exclusive photographer friend at IS told me the other day that one of the executives at Corbis was saying that the microstock market still counts only for 5% of the whole stock photography business. (Is there a market research on this?) This is a business which has the potential to go completely online than any other business. Much more than online music or movies. It means that we can expect many fluctuations including selling prices, new websites, disappearing ones, more stringent approval criteria, anything...
Although all seems positive for the contributing photographers, it may not be so for the individual ones, as big agencies discovered the potential of microstock. Look at iofoto.com. Now they have a portfolio of 10,000 photos on several microstock sites.
For now, some microstock sites still try to stay big by enlarging their number of images. Some seem to have more stringent criteria but still random, mostly influenced by the subjective opinions of the reviewers, the ratio of the number of reviewers to the number of uploaded images, unprofessionalism... These secondary factors still dictate the business. Even at IS, which seems the most professional of all, they changed the upload limits many times in a short period of time.
While the microstock sites, although some are already a subsidiary of a corporate business, are still struggling their way through technical problems, downtimes, staff shortages, they still rely upon uncontrolled costumer demand. I mean they do almost nothing to create additional demand. Direct mailing to existing stock photo buyers? I don't think so... While they started to implement better search mechanisms, lightboxes are not effectively used (as in the sense of stock CDs), nor the contributers are not effectively chanelled by the sites to take pictures/create images which have a higher demand potential. There is no business segmentation (for magazines of different sorts, advertisers, business sectors etc.). We are practically in the stone ages of microstock business.
IMHO, these will all change. But will those changes be to the good of individuals, I'm not sure. Some amateurs decided to be a contributor for a pocket money, then some even quitted their daytime job when they started to earn several thousands of dollars per month, but the introduction of photo agencies may change the picture.