I never said everything in the Other page is spam. I am saying they decided to dump any message that isn't your friend or (friend of friend) into the Others page, which solved for them problem of users seeing "spam" in their Messages page but created other problems.
You may never say that everything in the Other page is spam, but if you present moving all messages not from friends into a folder called Other to solve the spam problem...
Either you're going to have a horrible false positive rate or a horrible false negative rate, because sender email address is a really poor feature to determine spam from ham.
Jesus, why didn't any of these anti-spam devices, programs, companies, etc think of it! We'll just make a per user white list and be done with it!
Oh wait, that's a horrible idea, and you should feel bad.