The option to share stories to Facebook has vanished for me (again; it’s happened before). I’ve tried going into my settings and un-checking and re-checking the Facebook sharing option, with no luck. Also, the share to Twitter option is always available on my feeds, even though I don’t want it to be, and no matter how many times I check the box to add Tumblr as an option, it never works.
This happens on every computer I use, so I’m pretty sure it’s not just a matter of the cache needing clearing or whatever.