Hi,
I have thought of bookmarking and also something like a point of interest system where you can mark locations for later reference. However whenever I think about doing this I feel I'd have trouble making a case for it because you can just place a camera there. Managing multiple cameras is better in recent releases. I still think something like this could be good though.
A lock camera facility is not a bad idea, but it might be that all nodes should have a lock facility to avoid accidental changes, not just cameras. The beta will have undo support, so that will help to avoid the sort of catastrophic accidental change that you're talking about.
Regards,
Jo