Nothing contained in this post should be considered legal advice. If you wish to understand copyright, licensing, and all its implications, please read the sources yourself. This is a summary of my situation and analysis.
A few weeks ago, I got what might be considered a nasty message in reference to this site. In order to not put words in the author's mouth, here it is verbatim:
It's been brought to my attention that you are using one of my photos without permission on the following page:
I'm a bit annoyed as you never wrote to ask if you could use it. As it says on my profile: "Feel free to contact me with questions or queries. All images are copyright, and if you would like permission to use or purchase my photographs please get in touch. Please respect the fact that Flickr is a third-party website, and get in touch with me personally with enquiries about end usage of my photographs. thanks!"
I would ask that you kindly remove it from your website. If you had asked in the first instance, then I wouldn't have minded.
As an Open Source guy and someone who sells my intellectual property on a regular basis, I was taken aback. I work hard to ensure that all images, etc are used in accordance with the proper terms and conditions. Imagine my surprise when I looked at the Flickr photo in question. More importantly, I looked at what he posted it under (pictured right).
It was Creative Commons licensed!
Therefore, I wrote back:
The image has been removed from my site, but I believe you are mistaken:
You posted the picture in question under "Attribution", "Non-Commericial", "No Derivative works", and then linked to the Creative Commons – http://creativecommons.org/licenses/by-nc-nd/2.0/deed.en According to that license agreement, I (or anyone else) am allowed to share and use it as long as I give attribution, which I did via both the title of the picture ("War Room" taken by Fen Oswin) and linking back to the original Flickr page.
Therefore, I believe I am fully within my rights – under the Creative Commons License which you selected – to continue using this photo as I have not broken the terms. Regardless, out of respect for you, I have removed it from the site.
If you wish people to contact you and get usage permission, I would suggest that you switch the license to something more restrictive such as a standard copyright.
If you are a content creator and don't want people to use your stuff, make sure you license it properly. While just declaring something "copyrighted" may be sufficient in some cases with some people, labeling something Creative Commons and then re-defining it certainly is not.
Just like a photographer should know his cameras or a carpenter would know his tools and each would select the best for the job, you should know your licenses and do the same.