When you upload a photo to internet you do it knowing all the risks involved. But you have to present your work.
I had a problem only once, and I could fix it.
I always put a watermark, the upload never raise in the maximum resolution. I put the photos on a low-standar quality. If the website has the option to refuse the download, active this option.
Always put the copyright, register your work before you upload to any site or even before showing it to someone (you never know) and of course never give to anyone your originals! Remember your work is your son!