I can't share my xbox achievements on Facebook

That is actually half wrong and half right. No you can't share to twitter anymore. Yes you can still share to Facebook. The option is still in the dashboard, still listed as a feature, and very much still possible. I have no issues sharing achievements on
Facebook, just shared two to verify. However I get the same error message as the OP when I try to share Beacons to Facebook, again according to X-Box support still a viable and functioning feature.

http://dec.imghost.us/x9X3.jpg <--- Screenshot showing Successful Achievement Upload to Facebook

I've been having this problem for quite a long time, and sometimes it works and sometimes it doesn't.

No matter what i do though, I can't FORCE it to work... it always decides to work on it's own. I'm currently trying to share an achievement right this minute, and I'm getting the same error message as you.

Like you, I removed the two Xbox Live apps from Facebook then tried to share again, and it asked me for my Facebook email and password. I entered them, it accepted them. But it still refuses to let me share ANYTHING on Facebook, from the Xbox 360.

I've actually been sitting here for the past half an hour pressing the A button over and over, to select Share, then OK when the error pops up. 30 minutes and nothing. I have no idea what's going on with Microsoft, the Xbox 360 or Facebook.. but given how
many problems I encounter using Facebook, I'd say it's THEM that are the problem.

I'm getting quite frustrated now, to the point where I want to throw my 360 out of the window, because all I want to do is share a single sodding achievement and I can'r even do something as SIMPLE as that.

From Facebook, I searched for the App "Xbox LIVE" and authorized it to have access to my Facebook information. This included a step of logging in to LIVE. After that, I was able to login from the Xbox. I was able to share an achievement, but I had to enter
my FB credentials a second time, and authorize the post. Now when I check my authorized Facebook apps, "Xbox LIVE" appears twice, with different information under each. Anyway, as far as I can tell, there are no instructions stating the FB App authorization
prerequisite. The only clue I found was in the "Remove the connection to Facebook" section of the "Post to Facebook from your Xbox 360 console" topic, which mentions removing the application. Maybe if I had tried to share an achievement first, this might have
worked; I had only tried the Facebook icon on the dashboard.

So how can we share our XBOX Live activity on Facebook? I mean, when we get an achievement or something, an automatic post would appear on Facebook.

Then why was I censored all I did was share a video game achievement

I did absolutely nothing wrong in this case.

There is a feature that allows you to share your xbox game achievements

directly from your xbox onto facebook.