I'm sure you are very healthy and this doesn't apply to you, but someone else may happen upon this thread... salt craving can be indicative of addison's disease (a family friend was diagnosed).

I did a quick google search which (I thought you might find interesting) turned up the gamut of possibilites - salt cravings should be indicative that one needs to balance their electrolytes; salt cravings are false because the average person gets about twice the amount of sodium that they need in a regular diet; and (the best) salt cravings are experienced by recent alien abductees.