The news that Shutterstock has bought its rival BigStockPhoto isn't much of a surprise. In this market, being big is everything.

To be successful in this Web 2.0 world, you need to be an aggregator. It's hard to make money from generating original material. It's far easier to be the organisation that bundles together other people's material and skims a nice little profit off the top.

The microstock photo agency model is a case in point. Until recently, stock photo agencies - even ones that exist purely online, such as Alamy - made money for themselves and their contributing photographers by charging reasonable rates for the use of their images. In the traditional Rights Managed (RM) model, each customer specifies what it wants to use the image for and pays accordingly. In most cases, the customer can use the image only once. Payment could be anything from a few tens to hundreds or even thousands of pounds for such use. Photographers could earn a living wage this way.

Microstock agencies take a different approach. They charge peanuts per image. And they typically sell the images as Royalty Free (RF). That means that, while the customer doesn't 'own' the image, he or she can use it as many times as they like, wherever and whenever they like.

For the microstock agencies, it's all about shifting big numbers of images. Because the profit from each image is so small, it's important to sell a lot. (Las Vegas casinos operate on a similar basis, which is why they're huge, run 24/7 and host conventions to get large numbers of schmucks customers through the doors.)

By taking a small slice from milions of sales, microstock agencies make a tidy income. But that means they need to be huge - to have as many photographers submitting as many images as possible.

It also means that - overwhelmingly - each photographer makes very little. The math is very simple. Let's say an agency has 100,000 photographers each of whom has supplied 100 images. That's 10 million images. Now let's be generous and say that, on average, each of those images sells once over the course of a year, making $2.50 for the agency and the same for the photographer. Sounds like an equitable split, doesn't it?

The photographer makes $250. The agency makes $25 million.

Now, you can tweak those figures as much as you like - by saying that some images sell multiple times, that some photographers have far more than 100 images. But you'd have to tweak them to an idiotic degree before it starts looking like a good deal for photographers.

There are some exceptions - photographic hacks churning out reams of soulless photographic product to sell via microstock. But only a miniscule number of photographers can make any kind of living from this approach. And that means microstock will remain the domain of the amateurs who are pleased to get their images used at all and remain ignroant of how their work is being exploited.

It's easy to see why this market is also consolidating into a few, big players. The bigger you are, the better it works. That's why Getty bought iStockphoto some years ago and has since picked up Jupiter Images, with its StockXpert microstock operation.

We're fast getting to the point where there won't be enough money in stock photography to support genuinely professional work. But that won't worry the big operations whose only concern is the fast and massive turnover of 'product'.