This is a logical fallacy. You cannot prove something by eliminating what it isn't. No Sherlock...that which remains DOES NOT have to be the case.

Yes, it appears that the phenomena reported does not fit the attributes of anything we are aware of at the moment. That does not mean it must be aliens, although I wish it were true. :-)

The truth will not be found by eliminating possibilities. In fact even if we found one of these "orbs", dissected it and found strange writing and advanced technology that we could not explain - it would not prove it was "other worldly". Only that we don't know what heck we are looking at. Until a LGM comes to my door and points at the sky, ushers me into his craft and whisks me off to this God forsaken world, I'm still skeptical when people try to explain these things using false reasoning.

Having said that...I want to believe.