Just for the record I have found a tiny hairline fracture but it's not at the bottom (around the sockets) but at the back rim of this protruding plastic bit. There is a little hump on the rim with the crack on it. It seems to me that the poor quality plastic bit is snapped onto the main case and this causes tension leading to cracks over time.

Any kind of physical damage to my Nokia 770 due to misuse is out of question.

I suggest people check their N770s and report back here. This might give us all a better chance to convince Nokia that our claims are valid.