So let me give a hypothetical. Say my grandmother takes a really
awesome photograph. She doesn't want to create a Wikipedia or Commons account. In fact, she doesn't even have a computer. Furthermore, she doesn't want her name up on the Internet. But she is willing, after some persuasion from me, to license her photo under Sharealike 1.0.
Can I put this image in Wikipedia and/or Commons without lying?
I see no problems, just say "Created by my grandmother who agreed to license it as CC-SA-1.0."