I would also like to propose we don't allow reference links using domains that are not registered, or can't be registered (e.g. wrong TLD). The rationale is simple: reference links are meant to hold data useful for that entry. If there's no domain registered, obviously there's no data there, and worse, any random person can register it and put something there.
Also, I would like to then have a secondary policy of tagging reference data, when known, as not having the domain registered. This might lead to SEO spammers registering it, but they can do that anyways (e.g. walk the URLs, see if registered or not) just like I already did with a 4 line bash script.