Besides the Christmas timing, Yahoo quite recently upgraded the Delicious servers. Apart from whatever capital expense was involved, the occupation of the Delicious team in implementing the migration might have left them with the impression that they had a future. It's impossible to know in a corporation who knows what and who's blowing smoke for the company. Still, the tenor of pre-layoff comments from the team in their unusually candid support forum suggests that at least some of them were totally blindsided.