I probably sound really dumb posting this but...
I kind of don't understand why you need to clean them. I have never seen mine get dirty. I wipe them down once in a while with bleach just cuz it seems like the right thing to do.
How do they even get dirty? It is not like we touch them or anything. I spray the shower curtain down with bleach once in a great while, but again, it doesn't really get dirty. It usually tears and I get a new one after about a year.
It just seems like when there is so much to clean, that is the last place I would worry about. Nothing really touches it.
I am a pretty good housekeeper too. Am I just being dense?