Add on this that hardware sells also adds up to dividends in a variable way... it would be ridiculous to complain about a potential 14% variance, when the actual variance of dividends is much higher for different reasons.
Yes, over a week it is indeed not too important.
However, it would seem that it makes little sense to display 6 hour and 12 hour hash rate estimates on, e.g. http://www.asicminercharts.com/live/ . Even 24 hour estimates are quite unreliable: stddev of 26% assuming 10% network control, 37% assuming 5% control.
Or maybe the charts could be modified to include this standard deviation, so that the level of uncertainty can also be visualized?
I would think it would be trivial to include a standard deviation to the charts. A bar graph of 30Ths might benefit from a "+/- 2.43 Thz" disclaimer. If poll takers can do that, why can't we?