No excuse. It's the middle of January now, the holidays are long over, and they're one of the biggest companies on the planet. They had plenty of time to respond.
Yeah, making hamburgers! Out of 420,000 employees, they have all of 17 IT jobs on their career site.
They deserve a break today.
How many credit cards get swiped/waved per day at their PoS terminals? If they don't have a 24/7 infosec team they're Doing It Wrong™.
Conclusion: Bad excuse for a company this big, their communications being offline for so long is bad. But it is within reasonable to wait a little longer with disclosure, considering the mistakes made on the website, publisher should realise that the company hasnt put that much resources into this who security thing.
Public release was way too early, author should have waited.