When will people learn that just because you find a photo on the internet, doesn't mean it's yours to use as you'd like? On my main website, I've taken steps to (hopefully) make it difficult for someone to steal my photos - I've watermarked my images. I've disabled right-clicking images on my website (and included a popup box saying the image is copyrighted and to contact me for usage rights). I've included a copyright notice at the bottom of every page on my site. Does any of that help prevent theft? Apparently not.
While doing a Google image search recently on some of my photos, I discovered a blogger who was using one of my images (with no photo credit given, of course). I recognized the photo immediately. Despite my frustration, I preferred to give the benefit of the doubt and assume the blogger wasn't aware the photo is copyrighted. I decided to email the blogger a politely-worded Cease and Desist letter explaining that I found my copyrighted image on her blog, provided screenshots of my image on my website, and included an explanation of the steps I've taken on my website to protect from theft. I stated that if she wanted to continue using my image, here is my reasonable double-digit licensing fee for one-time use. Otherwise, if she chose not to pay that price, I asked that the image be removed from her blog. I asked that she respond by a particular date to avoid next steps being taken.
To my surprise, she emailed back soon after and my photo was removed from her site. I'm happy with the outcome and glad I approached the situation by contacting her directly. My other approach would have been to contact her ISP and file a copyright infringement complaint in the form of a takedown notice. (Good info on this process is available here and here.) Luckily it didn't come to that, but a couple fellow photographer friends I know have gone through this process when their requests to the copyright-infringer went ignored. In one case, the infringer's entire website was taken offline.
A few years ago, someone contacted me after finding one of my travel photos in a Google search. He explained that he and his fiance were from that city and they would like to use my photo on their wedding website and could we negotiate a fair price. I didn't feel it was necessary to charge them for the use of the photo since their website audience was mainly family and friends, so I gave my permission for one-time, one-website use at no charge. They went to the trouble to ask my permission and that meant a lot to me.
I certainly don't know all the details surrounding U.S. copyright law, but I do know that just because you find something on the web does not mean it's yours to take. For a fantastic in-depth article on photography and copyright law, visit Ken Kaminesky's blog. Oftentimes when I'm taking photos, I usually follow the "ask forgiveness rather than permission" mantra. Particularly when photographing inside public buildings or photographing people in a public setting. However, when it comes to whether or not it's ok to use someone else's content, permission really is better than forgiveness.