Facebook doesn't work like the other AddThis buttons. Instead of accepting parameters that we pass it, Facebook requests the URL you're sharing and gets the data it displays from the meta and link tags in the header. To control how your page is shared on Facebook you should use OpenGraph tags which are described in Facebook's documentation here: http://developers.facebook.com/docs/opengraph/
You also need to change the # symbol in the URL parameter to %23 or our server will think that it's an anchor appended to the /offer URL rather than appspot URL. Try this instead:
<a href="http://api.addthis.com/oexchange/0.8/forward/facebook/offer?url=http://ba-timeline.appspot.com/%234&title=Hellothere&description=Opis" rel="nofollow" target="_blank">FB</a>
<a href="http://api.addthis.com/oexchange/0.8/forward/twitter/offer?url=http://ba-timeline.appspot.com/%234&title=Hellothere&description=Opis" rel="nofollow" target="_blank">TW</a>