As a mail server admin myself I was always stunned by the accuracy of your spam filters. Almost no spam mail got into my Inbox and the mails found in the spam folder were almost always spam. The percentage of actual ham mails in my spam folder was very low.
I don't know how you achieved this very high accuracy of separating the good from the bad ones but you got it right. However, something's changed.
Since a couple of days now, I surprisingly find more and more actual mails to me in my spam folder. Real mails from real people. And some newsletters I am subscribed to, have been for years. With every day more and more mails are sent into my spam folder - and I don't know why. Did you change your filters?
The latest check of my spam folder a couple of minutes ago struck me: 6 out of 7 mails, tagged as spam, were actually ham mails:
Gmail, what's going on? I understand that a message from "root" or "Cron Daemon" could be tagged easily as spam, but the others? Don't know what you have changed but please revert it.