I've seen two flagsticks about 12 feet long.
One was on a Par 5 at il Picciolo, near Mount Etna volcano in Sicily. This hole (No. 6?) plays along a corridor that falls off to the left to another fairway 20 feet below. The landing area for the tee shots is well below the green, with the fairway rising to a flat shelf running up to the green.
My tee shot ended up in the short rough, and hit an iron to lay up to fairway. Next, I hit 7-iron approach into the green, a solid all-ball shot with nice follow-through that rose like a good iron shot is supposed to. But, it ended up 10 feet short of the green! The tall mountain flagstick was about 12 feet long, so I had through I was closer than I really was.
The second was at Kicking Bird, a public course in Edmond, OK. It was an early par 4 on the back nine. If I remember right, the green is behind a big mound in the fairway about 50 yards out. A person of average height would unable to see a normal length pin behind the hill.