I ran into this same issue ( PHP Notices all over FB ) this evening. While I don't know the cause, I have a workable solution. I've created a simple bot that will set the error reporting level to exclude notices. It's worked on my test site...
http://www.objectclarity.com/index.php?o...func=select&id=2
Install the bot then be sure to publish it and make it *LAST* in the bot ordering. It should reset the error reporting level and you should be good to go. Like I said, this isn't a long-term solution but it should ease the pressure.
Regards,
-4umfreak