I use the Cortech Sport Tail bag. I bought the FZ1 on 06/06/09 and I've already worn through the paint on the tail in several areas. I run the bungies through the grab bars and back up to meet each other toward the rider and in the back, through the grab bar and up to the clasps on the bag for the shoulder straps. I have 4 distinctly worn areas.
But I really don't care about it. As MarinaFazer said, I USE the bike. MY bike is a tool, not a toy. I bought it to ride, not be a street queen (Please, no offense to those that do keep their's pristine as I am not trying to slam anyone.)
When and if I am ready to sell it, I'll take the parts off, sand them flat and have a pro shoot them. While it is mine, she's going to take the bumps and bruises associated with my desire to ride.
That said, there aren't really any bags out there that won't do damage to the finish to a certain extent. You can get creative and find ways to prevent it, or, yau can strap the bag on, say screw it, and go for a ride! :thumbup: