Given the limited amount of data that can be displayed on a screen at one time, you should never have to wait. If the loading-wheel is spinning long enough to

Given the limited amount of data that can be displayed on a screen at one time, you should never have to wait. If the loading-wheel is spinning long enough to see, I consider that a bug. Yet a stuck loading wheel is pretty much synonymous with ajax. I see it literally everwhere I go. What gives?