The implication, and what makes this scary, is that if this were done with malevolent intentions, there could be a whole host of sites out there that had "bogus" certificates that Firefox would think were fine because they were signed by this trusted authority.
Just as an aside, you can always see the certificate chain in Firefox by clicking on the favicon area when a certificate is in use (i.e. when using https), clicking on "More Information", clicking "View Certificate", and going to the "Details" tab. You can then see the "Certificate Hierarchy". This shows you all the certificates in the chain, and who signed what. At the very top should be the "root authority"; this is usually someone like Verisign.
To bring this whole thing around, then, on some sites, you could see the root authority as the certificate mentioned in the post.
I guess, finally, I should point out, like others have, that this doesn't really mean anything bad is going on; the certificate could be perfectly valid. However, it is at least a little worrisome that they aren't sure where it came from.