Who's that coming over the hill? Is it a monster?
So, we know Donna is going to lose something and be important. Most people seem to be expecting her to die, but reset the Time War, or just the current situation. But I was thinking, maybe there's something else. Maybe instead of her life, she loses her mind...
Dalek Caan was sent mad by interfering in the Time War and rescuing Davros. If Donna also interferes in the Time War and rescues the Time Lords (possibly to save the Doctor from a regeneration that is failing), might she also be sent mad? This would certainly explain River Song's reaction to Donna. Especially if, in the process of doing this, she was accidentally made immortal like Jack, so she also loses her ending. This might affect the Doctor even more severely than her death.
Also, I've found out where the bees are going: http://news.bbc.co.uk/1/hi/world/americas/7482609.stm - the Canadians are stealing them and driving them round in lorries.