Cactus grows next to block

I experienced next to netherbrick as well, I stuck string on top for the time being but this seemed very odd when I first saw it. Didn't seem consistent though.

Shown here growing next to sandstone

I hope they keep this. It should attempt to apply damage but not affect anything that doesn't have a damage bar. Imagine cactus walls that are 1 block thick. Cactus pits that are just a solid sheet. Cactus on a sticky piston! Oh scratch that last one, it still needs sand below it...doesn't it?

And all of the cactus farms that just broke....

Initial testing indicates fixed in 14w04a