We've never heard of that issue before, so I don't have any great answers. Can you check if your computer/browser has an addon installed to hide your social networking activity? Addons like Ghostery and others have the sole function to hide social features like you're mentioning, and being logged into Facebook may be triggering that.
Beyond that, all I can suggest is:
* Try from different computers, browsers or Facebook accounts and see if you can narrow down anything common that may be causing the problem
* Let me know a URL where we can test and we'll try ourselves.
Thanks,
Alex