Good points Egg. It had not occurred to me about a disgruntled member changing an image to include any of the above. And I have no reason to doubt that that could happen. Steady and level thinking like that is why you will be missed.

Frances - In order to increase the resolution of an image to anything approaching print quality, the image has to be very good to begin with. You can use Genuine Fractals to upsample an image and get OK results. I have done it with some of my 300dpi TIFF no compression stereogram images to increase the size for larger prints, and it works pretty well.

But I have also tried to enlarge some pretty good JPEG images saved with 20% compression (80% Xara Quality setting) and the results have been unusable.

For images posted on the web at 96dpi to be usable for commercial printing, they would have to be reduced to 1/3 the size to achieve an acceptable print resolution. So an image that is 6" at 96dpi needs to be printed at 2". Not all that useful.

The bigger problem with images on the web, is they can be copied, usally you can drag an image out of a browser and drop it onto the desktop. Or a screen capture for Flash sites that do not let you copy the image. And these images often end up in the portfolios of people with no talent who want to show their Facebook, or other social networking sites how cool their taste in art is. A few years ago I spent a few weeks contacting a large number of social networking sites asking that my images be removed. And the burden of proof is on me, not the user. This is why images posted on the web should all have a very visible copyright line. It is very hard for Jane Doe to post one of my images and claim it is hers. Unless of course the person removed your copyright line.

The sad truth is if you post an image on the web, and somebody likes it or wants to use it, they generally will. And very few persons will have the decency or honesty to request permission to use an image.