Image on web published in full resolution resized in code.
Imaginary (to keep it simple and short) case:
You sell your absolute favorite image for a one time, non-exclusive use on paper in a magasine and their website version.
After a year or more you discover that the magazine has in their wisdom uploaded your 7000px masterpiece to their website and resized it to 700px in code. Apparently noone in the company can figure out why the image loads veeeeery slowly on their page.
In other words, any Tom, Dick and Steven who don`t possess any morals, can not only steal your nice little 700px image, but the whole thing in full resolution. And use it in every way possible.
So your question is: How much can you charge, relative to the selling price for this little mishap?
Image: Illustrating the difference in resolution.