I'm not sure how they did it, but overnight my Google account storage went from about 70% full to 110%. Big red warnings tell me that my photos won't be backed up and I'll soon lose the ability to receive email - unless I start sending Google money every month for more storage.
I tried deleting all Promotions emails, but after I deleted them all they were all still there and my storage was unaffected. I deleted my largest video, which in itself should have brought me well below 80%, but that too had apparently no effect.
My guess is that Google has decided that it's time for them to leverage their monopoly to just outright steal from the peasants.