i agree steve ...
that is the difference between looking at an image / " personal use "
and someone either hotlinking your image to their website, or ebay selling page
or an ad agency snatching an image off of flickr or wherever it might be hanging out
and using it in an ad campaign. there are digital watermarks ( like digimark )
that allow photographers and painters &c to embed a homing device
into the image to track where and how it is being used.
i have had trouble in the past with a very large and well known real estate developer
retaining my work ( without paying for it ) and publishing it without my consent. as you said
that it a lot different than a photograph of cute puppies, or a slick cityscape, or hollowbody telecaster
someone found on flickr and has on his/her computer in their rotating screen saver.