Lately, it has come to my attention that we seem to be seeing a new kind of spam that contains only subject lines and empty body text, or limited body text.
These types of spams are tricky in nature because we don't yet know what the deal is. Why would anybody send this type of spam if it contains no contents? Certainly there is no payoff for the spammers.
In my opinion, these types of messages are usually pre-cursors to big spam runs. I don't know if the spamware is broken or these are quite intentional and a spammer is just testing to see whether the spam will bounce back. In any case, in my experience these types of things are typically followed by big spam runs usually less than 48 hours later. In most cases these are stock spam runs with embedded images that are a plague upon the existence of civilization. On the other hand, at least we're learning from these things and can get prepared for when they hit.