I don't know if it is common, but the problem is that these links are for off site so the webrep tends to check them in the same way as a google search.
This used to happen in wikipedia before even for internal links, but as far as I'm aware they changed how it worked in wikipedia and external links don't get the webrep treatment.
I don't know if this should be treated in a similar way, but given the nature and risk in facebook, personally I think it should remain as it is.