What happened to my Favorites list? Every single addon that I had saved from this site is now gone. It was there last night when I came to check for an update to Skinner... now the entire list is gone.

Are they still gone?  They should have dissapeared for a small window around 11:00 while they were migrated to a new system, but should be available now.

Additionally, this migration enabled bulk (digest) notifications for favorite addons.

Yes, they are back now.