Suite du ./3199 :

I just attempted to browse my Facebook Page's messages in app. Gradually my computer slowed to a crawl. Task Manager revealed that every time you click something in Page Messages (e. g. Delete message, Archive message, switching folders, or just entering and exiting selection mode), a new Facebook process is started. Which is a browser process because the last one loaded without the CSS all Times New Roman-y. These processes all eat 50 MB of memory on average.

Then I got an error message with a link saying "Back to home". Clicking it took me to the News Feed but with a very different layout. It had a "This website uses cookies" notice on the top.