Dreamstime celebrated their 10 millionth image with a day long 20% discount sale for buyers and 100% commission to contributors. This brings a total of 3 microstock agencies with more than 10 million images in their own collection (so pixmac excluded). 123rf looks like it will be next in line.
In tandem with last months site updates and introduction of $1 images, Crestock relaunched themselves as "Good. Fast. Cheap" at the start of the month. Their previous price levels and site style placed them more towards the premium end of microstock.