I lost one of my System Cases last year. I had removed the cases to wash the bike (that'll teach me...) and when I put the cases back on, I must not have correctly lined up the lower mounting tab / ears. I left the house, headed up Highway 9 and when I arrived in San Jose, my left case was missing!! Dang. I went back over Highway 9 to try to find it but no luck.
I posted a "missing bag" report and someone said that they'd seen one at the Hwy 9 / Skyline intersection parking lot. When I got back up there the next day, nothing to be found.
I rode without for a year and then bought a pair (with City lids, not the touring lids I had before) off of the Flea Market portion of this site.
The up-side was that for a while I rode with just a right-side case and the left side mounting rail has a nice place to thread your helmet strap through when you leave the bike. Not totally secure but better than just hanging it off of the foot peg.
Now I ride with a Touring Case on the right (my lunch box fits perfectly inside) and with a City Case on the left. It's not symetrical but it's a working compromise for me. Heck, I don't ride a Harley so I'm not all that concerned with looks or what others think anyway.