I was up and fine and stable and sometime during the day I have lapsed into 500 errors on the admin side as well. While I can't guarantee it's this plugin, it seems likely, as things like the recommendation bar (which was enabled) have "vanished" from the front end.
Unless you count Digg Digg, I do not have any other FB related plugins. However I do have full comprehensive opengraph tags manually added. That was not causing me any issues earlier in the day.
I'm going to manually down the plugin as soon as I get to a computer (on my phone at the moment) where I can use my private keys to get in. However, it would seem that my opengraph tags are upsetting the plugin (or something else is).
I'm not sure I WANT to remove my opengraph tags as they carry a lot more information than this plugin yet gives us fields/tools to set up.
I know this is an incomplete report, since I haven't downed the plugin yet, but I wanted to contribute the information on the OG tags asap.