> companies have decided that 3 = Bad, 5 = Acceptable.

Does Uber actually give instructions on how to rate? Does it say a normal, acceptable trip should be 3 or 5? What would a really great trip be anyway, perhaps if the driver says "hey, I just won a lottery and I'm celebrating with my passengers, take $10k", or perhaps something sex related?

Once Uber kicks out all the below-average passengers / drivers, will they take into account that the average will be pushed up for those remaining, so they will need to do further rounds of kicking?