When people share a Wikipedia article on Facebook, it often shows the MediaWiki logo (instead of more reasonably showing the Wikipedia logo). I assume this is the case for other projects as well.
According to Lars Aronson, this results from the MediaWiki being the last image entered in the site CSS. He suggested altering the CSS to include the Wikipedia logo at the end, here:
http://www.facebook.com/pete.forsyth/posts/569979664118
(see also bug 39842 - seems related)
Version: unspecified
Severity: minor