Unfortunately once you publish your photographs you will find they will turn up on other sites without a license and there seems to be a general feeling that photographs should free to use and people can just help themselves ignoring any payment or license conditions.
A lot of countries have a system of statutory damages including the US which means the photographer does not have to prove loss just show that their image was used without a license.
The value of the photograph may be taken into consideration but statutory damages are also there to act as a deterrent otherwise people could just take images and when discovered simply offer the license fee.
In the US there are three levels of statutory damages for photographs registered with the copyright office.
1. Innocent Infringement – range $200 – $750 per infringement plus attorney fees and costs.
Innocent infringement covers cases where the infringer had reason to believe that they had a license to display the photograph. For instance the infringer may have purchased a license from a person or organization they thought represented the photographer and it turned out not to be the case.
Innocent infringement cannot be claimed by infringers who simply copied the image from a search engine or a site offering free images and the infringer must show they made reasonable enquiries to determine that they could use the image.
The onus is on the infringer to prove that their infringement was innocent and not just careless.
2. Infringement – range $750 – $30,000 per infringement plus attorney fees and costs.
Most infringements fall within this category when the infringer has simply taken the photograph from another web site or from a search engine. The photographer does not have to prove any intention in the infringement just the facts alone are enough.
3. Wilful Infringement – range $750 – $150,000 per infringement plus attorney fees and costs.
Wilful infringement covers cases where it can be shown by the photographer that the infringer should have known the image was subject to copyright and simply ignored the fact or else was warned about the infringement but carried on using the photograph anyway.
Should an image be clearly marked as subject to copyright or the text around the image clearly demonstrate the copyright of the photographer then the infringement may be considered wilful.
The photographer has to prove the infringement was wilful.