I am a sports photographer and I own the rights to all of my images from colleges throughout the region.
Everyday I go online and see various newspapers, students, and other web sites using my work. It is all copyrighted, but it is almost impossible to contain it once is it let loose on the world.
Some places are really good about protecting my rights, but others don’t care. Students, parents, and others think that if it is on the web it is free—so they just right click away and paste it all over facebook and other sites.
I find that most of these people are not malicious, just ignorant. But, my pocket is hurting from a sharp decline in secondary market sales (families, friends, and the athletes themselves.) We are down nearly 80% since the peak in 2007.
I’m a writer. I’m not sure there’s any value in trying to protect stuff available online.
Do you have a website up where people can access your photo shoots?
That's quite different. In your case at the very least I'd get a form-letter DMCA takedown going to their ISP. Beyond that I'd register the work and then at least for every for-profit infringement I'd sue for statutory damages. Going to court with the registration in hand and a copy of their web site is pretty much an open-and-shut case if they used your photo in-whole and for-profit, without the usual exemptions like commentary and parody.
On the other hand, would you sell a person a copy of one of your photos and then say you have the right to pull it back at any time? That you can prevent them from showing it to too many friends? That they can't sell it again to another person? IMHO that's abuse of copyright, and it's becoming all too commonplace these days.