
Aid workers in Dadaab - the world's largest refugee camp, set up in 1991 to cater for Somalis fleeing civil war - tell me that families always ask for cylindrical jerry cans rather than ones with square edges. The reason is simple. Five-year-old daughters cannot carry a can filled with 20l of water. But they can roll the round ones.

Rob-
Great stuff both here and on Twitter.
You might find this interesting: http://twitter.com/HippoRoller
Their site is down right now so their Twitter link is all I can offer.
Cheers,
Jon