evidently there were only 4, and they never even boarded the plain, let alone checked luggage in. 3 have been identified and they all just missed the flight.
http://www.news.com.au/travel/travel-updates/the-tweets-from-a-passenger-who-claims-to-have-missed-boarding-malaysia-airlines-flight-mh370/story-fnizu68q-1226852311845
