When you share an interactive panorama on Facebook or Twitter, it's only a link with the title, thumbnail, and maybe description that points to the view page here on Photosynth.net.
Sadly, Facebook does not embed photosynths or panoramas from Photosynth.net nor does Twitter support them in expanded tweets.
Whenever I have shared a synth or a pano to Facebook, the link appears in my timeline. If you want to double check whether the app is posting the link to your wall, check your activity feed. Maybe your Facebook settings just aren't highlighting links from Photosynth on your profile.