Being the devils advocate here...
From an economic point of view, such dealers and incomplete ads create curiosity, curiosity creates hits/visits/traffic which help generate revenue for this site; not to mention dealers probably bring in revenue via commercial advertisements/sponsor.
It would be in the forums best interest to NOT discourage dealers, but at the same time imposing a bit stricter guidelines and not having a 'call' option would definitely be a good idea to keep the members happy.