typophile - 2:03 pm on May 22, 2001 (gmt 0)
Visibly watermarking an image with a logo will mean that the user can download it but it will be unusable. In any event a 72dpi jpeg is useless for print reproduction and can really only be re-used on the web. In practice most artists have no problem puting their work online for this reason. Plus if the image is re-used (with your name and url watermarked into it) it is just more free publicity for you.