Tried to add the widget to my side bar, and it only shows a blank line.
Upon returning to my sidebar menu to remove it it appears as blank and just a [x] to remove it. Clicking the [x] doesn't remove it, it's stuck there. I tried adding a new one, and removing and that went fine, it's just the FB one that seems to have this problem.

I DID manage to remove it by manually typing in the removal link: http://subeta.net/preferences.php?act=sidebar&wact=delete&widget=5
(users would have to decide which number to put on the end, my case it was 5)

I discovered when hovering over the "empty" facebook widget removal X there was no link like this at all (it only linked to the side bar page, not a removal link)

That may be so, but it is very difficult to remove from the side bar if anyone tries to for the achievement (like I did). Perhaps it should be disabled from the sidebar menu as well?