I've always had a problem with horizontal surfaces, but recently I toured a couple of manufacturing plants that really highlighted their danger. Yes, "danger."
Many operations have implemented 5S programs to help improve workplace organization. A place for everything and everything in its place. These programs can do wonders to reduce the time it takes to find tools, equipment, raw material, and paperwork... thereby reducing total cycle time and freeing up floor space... thereby creating capacity. But let's apply a little root cause analysis to determine why some aspects of 5S were required in the first place.
For example: "Why" are we capacity constrained? Because we don't have enough tools. "Why" don't we have enough tools? Because they can't be found. "Why" can't the tools be found? Because they were not returned to the appropriate cabinet. "Why" weren't they returned to the appropriate cabinet? Because they were left on top of the piece of equipment they were last used on. "Why" were they left on top of the equipment? Because it is a horizontal surface. Therefore horizontal surfaces contrained production capacity.
Ok, that's a somewhat skewed example, but the point (no pun intended) is still valid. Horizontal surfaces have a tendency to collect tools, paperwork, parts, discarded gloves... you name it. How much cleaner, neater, and therefore more efficient would our operations be if we could get rid of non-essential horizontal surfaces?
And that's how I justified a new flat screen TV for the bedroom at home... to get rid of the nice wide horizontal surface on top of the old CRT TV, which was a convenient "in transit" point for clothes...