Good, why? I haven't seen this adequately explained. Considering we are not even reaching capacity at 1MB, 8MB is completely arbitrary. 8GB is beyond arbitrary -- it's simply out of touch with reality. The only possible justification is Moore's Law, and as I pointed out above, this is an illogical and unscientific basis to go by.
i dont think it is needed to proof whats the best minimum. imho we need to show what is a good possible max.
no one can see in the future. this means we cant know how much blocksize we will need. but we can make educated guesses about what might be a good max. and if we are wrong with that maximum lets just have a little trust in miners which dont want to let bitcoin fail to choose some reasonable value.
yes 8mb is arbitary. but why is this a problem? it is not possible to calculate the future (at least for now and not from inside our universe). what transactions are put in a block and which arent is a decision made by people who have the incentive to keep this system running.