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?
Why not? If you ask me, just say so. Good enough. If you don't want to use your name either then use a throwaway account, and say so.
I'm pretty sure I've seen things like this (for public domain rather than CC-SA).
Dan