A few snippets that may help...
Copyright lasts 50 years. Even if the author dies, he still owns the copyright through his beneficiaries.
In the UK at least, you can quote up to 10% of a book in other publications, as long as the sources are acknowledged.
Quote: "if there is no copyright watermark on media/information then legally it's free game."
I don't know the finer details, but that is plain wrong! You don't even have to include a copyright statement for something to be covered by the copyright law.
For someone to claim copyright on a copy of an original piece of art, such as Da Vinci's last supper for example, then I would imagine that it would need to be a derivative of the original. So simply scanning the image would not make you a copyright holder. But if you then retouched it and removed all the blemishes and cracks, yo could probably claim to own that derivative of the image. The bit I miss here, of course, is whether you're actually allowed to copy the image in the first place!