Ya they will fall down if you dont use motar depending on the use you can fill all the hollow spaces with concrete for like a safe room or tornado shelter however in most cases every 4th or 5th cell is filled solid with concrete
LOL, that's awesome. But a nice FAQ list would have probably saved this guy tons of time. Write down the top 5-10 questions people ask you in your ad/auction and you'll not only save a lot of time answering emails, you'll probably increase your sales.