Sites like Flickr have been growing in popularity for the last few years. Taking photos and uploading them to sites like Flickr has been a hobby of many enthusiasts. Unfortunately, some people try to take advantage out of it, and are selling pictures taken from Flickr on sites like eBay. Usually, they claim that they are their own, which of course is not true. It is not easy to identify such people, and even if you are the one who took the pictures, it will not be easy for you to track each photograph you have made. Even if you are using some tool to detect duplicate images, it is easy to change the size of the picture by slightly cutting the bottom or right/left side of it. This way it should be impossible to track whether your photos are being posted anywhere else. Your best bet is to watermark your pictures.
Of course, if you are taking pictures simply for fun, then you are not going to lose any money because someone is selling your pictures. If would be a completely different situation if you were a professional photographer because people who downloaded your pictures from Flickr could undercut your prices very easily. That is because they would have no costs associated with downloading your pictures. I am not saying that sites like Flickr are a bad thing, but I am simply reminding everyone that it is easy for people to take someone’s work and claim it as their own.