Creative Commons licenses have become popular in the past few years and are included in Flickr as an option for your own photos. What you may have not noticed that you cannot actually specify that your photos be totally free and thus part of the "public domain". This is the way a government may want to release information for completely free re-use, without attribution, etc.

Flickr's reasons are interesting:

(i) Unlike CC licenses, you can't take PD back - once it is done, it is done. I spec'd out a three stage confirmation (including typing out that you understand what it means) but this was seemed like too much and we didn't want the support hassle. People are free to use the description field to specify their PD desires.

(ii) There are liabilities that we don't want to take on if we allow people to claim something is public domain without actual checking the chain of title - if they don't own it in the first place, we can get in trouble. (This is also true of CC images, but at least that can be changed after the fact and there is less of a chance of the image just "escaping" in the wild.)

What do you think?