DSF

I can't understand why so many photographers put large images on the internet without watermarking them. They must be bloody stupid. Images like these are crying out to be copied. So I think some of the blame rests on the lazy copyright holders.

As anyone who has ever tried to remove a watermark in Photoshop will know (er, ... so I've been told!), watermarking is the way to go to keep your images from being copied. The onus is on YOU!

Put large images on the internet. Do a search for your images, send an invoice/ legal letter for unauthorised use. Collect winnings.

Yep. Some of the large stock photography companies make their money that way as Gooner says. Make them easily accessible then have a program crawl the web to check who has jumped on the bait.

I can make money on Amazon and not sell anything

Since most of these images are stolen for commercial use, it becomes flagrant copyright infringement. You can request an uplift in damages well above the normal cost of a licence.