Not to sound like an ass, but it's going to last them longer than no extra drives from the campaign. So it'll certainly help them along :-)

You don't sound like an ass!

I was just wondering why something which is almost universally seen as good (or great, even) is running donation drives to get 4 petabytes. (To bring them to a total of about 14 petabytes.)

(I guess I'm comparing to Megaupload's 25 petabytes - which are still(?) sitting in racks not being used.)

Not sure, but for comparison, they're currently using 10 petabytes.