I wouldn't take it too seriously. No one but the higher up apple employees would know anything about it, and they all know better than to tell someone.
You probably got unlucky, think about how many people pick up those MBA's at the store and mess around with them, balance them, etc. When you buy a new one, it is incredibly strong.
The joints on that machine were probably worn down from all of the use.
I'm not sure we're talking about the same 'lower right corner'. I held it up by the right corner near where the trackpad is, not near the hinge. Maybe it is due to some wear or maybe it wasn't the entire chassis flexing, but there was definitely some give there in the materials. Also, of course, the MBA screen wasn't closed either, so I literally held it from the thinnest possible corner.
Of course, I never lift up any of my laptops like that, but then, none of my laptops are that light either, so never had the urge to.
The real question that Apple is asking is "would it buy someone?" I feel that answer to this question is "hell yea!" but I don't think they will release 15" air so soon... Maybe in future