There is no way to prevent someone from stealing something they really want, be it your car, your plasma tv, or your images. But there are things you can do to make it hard and to really nail them legally if they get caught.
1. Register your works with the copyright office. You can do a group registration of thousands of works. John Harrington has written about this extensively in his book and on his blog (
Photo Business News & Forum)
2. Use the meta data options afforded to you to place copyright notices and author information on your photos. Does the average person know how to read meta data? No, but the people who should know better do and if they do infringe on your copyright it makes it a lot harder for them to say "Gee, I didn't know whose it was" BTW, the upcoming Orphan Works changes to the copyright law make this very important.
3. Don't sweat the small stuff. If someone uses one of your photos on their myspace page, be flattered. It's not costing you anything, you're not losing a sale (no 13 year old is going to license your photos) and you've made someone happy for 15 seconds. If someone takes your photo and publishes it in a magazine, call your lawyer.
If you've registered your work within 90 days of creation, it's legally considered registered at creation. Realistically, if an image has been infringed after registration it's worth pursuing, since you can claim attorney's fees and punitive damages as well as compensatory damages.
Bottom line, register your work. Every image you show to anyone (other than your mom) gets registered. If that means every month you register 755 images, so be it. $45 per registration(not per photo) is a small price to pay if you're serious about protecting your work. If that's too much, then why bother?
SB