I know from time to time images have been lifted from this site and pasted into commercial petro websites and that is just not right nor is it fair use. And because OLDGAS has a clear disclaimer about images created/taken by members being their copyright, no one can claim 'they didn't know!'
I used to teach and used images in powerpoints. I always asked, and always, always gave credit as a caption of who took the original image including and especially if the author of the work considered it copyrighted.
For example:
Used with permission, Copyright 2010, Joe Shmoe
If the source material said limited use for educational purposes acceptable I usually did not need to contact the actual photographer but would put something in the credits like this:
Copyright 2010, Ohio University.
The images were for a small group (my class) and I never posted them on the internet.
If I was to change the use (ie advertisement for a class in some brochure or on line) I would try to have original photos that I took, before asking someone about sharing anything on the web, and in fact I think few photographers would allow that kind of use.
UtahBob, I think as a curator, if you are going to use current images at your museum, it's a good idea to always ask first. And if they say no, there may be someone else who is willing to provide you their image. Make sure they are clear on the extent of your use, and get their permission in writing.
I do the same with models I paint, always have them sign a model release form that spells out that I will have copyright to all reference photos and the final painting and that the painting will be for sale to the public and an image of the painting is a part of my portfolio.
I know, I know TMI Hey I'm waiting for my laundry to dry!