Strategically, in politics and in
PR, bad news is disclosed on a Friday afternoon at the end of the weekly news cycle, so that By Monday's cycle the initial furor will have worn off somewhat.
If Apple waits 'til Friday, I foresee a not-so-favorable rebate with alot of conditions: one per customer, not applicable to ipod, imac, i-anything good, etc., etc.
Just speculating.