The command "/summon FallingSand ~ ~ ~" used to summon a FallingSand entity that would disappear before falling as its "Time" was set to 0 by default. This function could be used to create motionless enitities that would appear as blocks but could be walked through when adding a certain "Motion" and repeating the command with the use of a fast redstone clock.
In snapshot 14w06b the default "Time" of a FallingSand entity summoned by the command "/summon FallingSand ~ ~ ~" is no longer 0. I discovered this when the "hologram" I created using the technique I mentioned before was falling. Even when changing the command to "/summon FallingSand ~ ~ ~

" the FallingSand entity would still fall. I have searched the internet for any alternative ways to create these "holograms" but all the techniques I found involved spawning FallingSand entities with there "Time" set to 0.
I don't know if this change was made intentionally. If it was, I'm sure you had your reasons. But if not, I, and probably other mapmakers as well, would greatly appreciate it if you would fix it by changing it back to how it was in earlier versions.