Jerseyjim- Hopefully Ortlieb can help you out. Their explanation seems spot on and like it would be an easy fix.
djb- To clarify, I have never had this happen to me, because of me. I received the bag from it's previous owner with the one snap pulled out. Once I separated the snap and stuck it back in the hole it came from I have not had any more problems. But this is a non issue for me because I rarely fully snap close the top.
The updated design for 2013 seems like a good thing. I hadn't even thought of magnets, but they would work well for one handed opening.
I cannot stress enough how much I love my handlebar bag and could kick myself for not buying a decent quality quick release one earlier. If any one is reading this and wondering about a handlebar bag do not let these small problems stop you from trying one.