maximillianos - 1:51 am on Jan 17, 2012 (gmt 0)
The emails are probably going out in batches. You can't just send 24 million emails unless you are Google, Yahoo or Microsoft and are sending them to your own email users. :-)
I had a simillar issue last year. Had to send an email to 100,000+ users. We did it over the course of a week due to restrictions from our email service provider. It is very difficult to try and notify so many folks.
The worse part is yet to come for them. For the next 6 months if any of these 24 million have their identity stolen, have a mysterious charge on their credit card, can't access their email, or any other strange out of the ordinary occurrence.... They will be contacting Zappos to complain.