EXIF is not IPTC metadata - see http://www.exif.org/ versus http://www.iptc.org/photometadata/ and so on.
Let's open a can of worms!
No ... let's write an extension to, or core for, MediaWiki that only permits successful image upload when all metadata is filled in on a web-form during submission, and that form's blanks get:
(a) automatically read from metadata within images that already have it at the time of upload; and / or
(b) gets that metadata inserted by the end user / submitter for any data that is missing; and
(c) contemporaneous data gets inserted, such as IP and date and user ID.
I have my camera automatically put "peterblaise.com" in the EXIF of my images immediately during the making of even the latent image (that's when my copyright happens), but many image converters strip out EXIF and IPTC metadata. Many people superimpose their copyright IN the image fascia, but cropping or cloning can remove that, and too overwhelming a copyright notice changes the image and often makes it purposeless. Rather than contact you with a credit card (are you even ready?) for a non-watermarked copy, and await your response, they will move on to a non-watermarked image.
The world's most popular free Google Picasa strips metadata at the time of export and replaces it with "Picasa" in the "Byline:"!
That newspaper should never have published that image without having, and being able to provide on demand, an audit trail of it's origins. If Joe Reader sent it in, then the newspaper should have that audit trail, and then Joe Reader is the one to sue (civil) for compensation, and also complain to the authorities (criminal) for prosecution. If the newspaper uses Picasa and just publishes anything it wants, it should be confronted on both civil and criminal counts.
Back at ya:
Q: How can any of us prove the picture was ours before someone else publishes it?
A: http://www.copyright.gov/register/visual.html
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Q: How to insert IPTC metadata in our image files before distribution?
A: http://www.photools.com/ and hundreds of other controlled vocabulary IPTC-compatible software - see also http://www.controlledvocabulary.com/
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So, cc: wikitech-l@lists.wikimedia.org is anyone up for developing an extension or core code to make MediaWiki accurately handle such MEDIA as photography and images with EXIT and IPTC metadata? Sound recordings can't be far behind. Spoken work and music are ripe for cataloging wiki-style. Will it be MEDIAWiki style?
cc: also to http://picasa.google.com/support/bin/request.py?contact_type=testimonial