As Shutterstock library is approaching 10mln, I thought you would be interested in how that compares to the competition. So, a quick lookaround, and here is the chart showing how it all compares (as of 9 feb).
Unsurprisingly, Shutterstock leads the pack, followed by Fotolia and Dreamstime. Both has recently raised their acceptance bars, and the gap is likely to increase in the mid-term. Shutterstock, according to what I observe through microstock forums, has a relatively loyal acceptance criterias, so is likely to remain number one with their Portfolio size.
But microstocks are not the only players in image market. There are also macrostocks (traditional agencies like Getty, Corbis, etc) and photo-sharing sites, most famous being Flickr. I will do a separate research on them later this week. Stay tuned !!