I agree with commandblockguy. One of the main goals of craftbukkit (not spigot) is to avoid making changes that break vanilla behavior; this is a vanilla behavior that is sometimes useful (albeit also problematic). Getting rid of it without any option breaks a small selection of vanilla things, which goes against that goal.

(For reference, craftbukkit commit 616a9687 changed this behavior, and the vanilla ticket is MC-90523)

https://www.xkcd.com/1172/

This behavior has some uses in both aesthetic and functional designs. For example, some creeper and witch farms use falling sand entities to remove arrow entities which would pile up otherwise. It is also used to make slabs out of concrete powder which are not normally possible, such as in this video here https://youtu.be/pQvOsOa0Vl8?t=1m39s

This fix should have a configuration option so that players on servers without security concerns can use the vanilla behavior.

Fixed on our end because it's a reasonably serious issue

You can use this technique with torches too. Actually much faster to clean entire sand areas using torches than fences. We just filled in guardian temple with sand and used this technique to clear out most of the water to turn it into a fish farm. Also found extremely high entity count during the process. We stopped halfway through and went looking for people breeding too many cows or chickens. Now it's really funny that the whole time it was us duh lol.

The fix is pretty simple, but it's likely this is intentional. Gonna try and find out why Mojang changed this.

Falling sand is an entity, so that you can cause massive client lags and make some chunks inaccessible.
In 1.8 the block stopped 1 block above the fence and wasn't in state "falling", now it's an entity that stays in the "falling" state if you let it fall above a fence.

Whats the issue, it breaking and making items or what?