There is always a difference of opinion as to whether images displayed online should be watermarked or not. Some feel that watermarks spoil the viewing experience and that they would prefer to see images without - this can certainly be the case with very large or prominent watermarks. Image creators on the other hand, want to protect their images and prevent them from being used without their knowledge so by adding a watermark, they can at least show that the image is legitimately theirs.
It is a sad fact that a lot of web users seem to think that it is acceptable to take images, music, articles and other intellectual property from others, for their own use and don't feel that they should have to pay for it. Those same people however will often be the first to shout when someone else uses some of their content or the derivative works that they have created using the work of others. Copyright law is, in my opinion at least, unnecessarily complex but ignorance is no excuse - if its not yours, don't take it.
Most watermarks are easily removed of course, as is the metadata which is embedded in all of my images but the very act of removing a watermark, or the metadata, shows that the person doing so is aware that they are taking someone else's property - it is a bit like finding a wallet and removing the name and address of the person it belongs to, pretending that 'finders keepers' applies. They might remove the evidence that it belongs to someone else but they know what they are doing is wrong.
So how do you stop someone taking images or other content when online?
My own view with regard to watermarking is that of compromise - by placing a discreet watermark I am laying visible claim to my image but hopefully without spoiling the experience for someone viewing it. By using my website address, it does at least provide some means of identification if found on another website and hopefully other viewers will come here to see more. The images used are low resolution so won't be suitable for printing at anything larger than snapshot size and even then won't give a very good result. So, if someone wants to take it, go ahead - just leave the watermark intact!
Once the watermark is removed however, things change - the only reason anyone would go to the trouble would be if they want to try and gain from it, either commercially or by passing it off as theirs to use on their own website or portfolio.
If you want to use an image, please ask and we can agree terms. I will pursue and invoice for any copyright infringements or unauthorised use.