weasle, Monet and others who were wondering about 'offloading' passengers, I mentioned upthread that it would be impossible to open the plane doors at that altitude (even the emergency exits) without depressurising the cabin first, so it's unlikely that any potential terrorists would have bothered, given that they'd then have to wear oxygen masks for the rest of the flight. If they were hijackers then presumably they were armed, so if they wanted to kill the passengers there would have been easier ways to go about it.
Isn't 45,000ft fairly standard for a jetliner? On the high side of standard admittedly, but I'm pretty sure some do go up to that altitude (not sure about a 777 specifically). Given that the cabin's pressurised anyway I wouldn't have thought the passengers would be too badly affected, provided the plane itself wasn't damaged. I'm not sure about that though, someone correct me if I'm wrong!