Another interesting list would be all those products where the originators thought they would be used for one purpose, but their users invented other uses for them. Two examples that spring to mind are SMS and tape cassettes. The classic example is 3Ms Scotch Tape. Donald Schon describes it thus:

"I once did a study at 3M [Minnesota Mining and Manufacturing], observing how they went about developing new products. Do you know the Scotch Tape story? Scotch Tape was a World War II product, invented by Brandon Cook in the 3M laboratories. He had the idea that you could use transparent cellulose-acetate ribbon, with pressure-sensitive adhesive on it, to mend books. And since you could mend books with it, you wouldn't have to throw the books away, and you could save money; hence, the name Scotch.

When 3M put the product out into the marketplace, it discovered that mending books was not the only use that people had in mind. People did bizarre things with Scotch Tape: they wrapped packages, hung posters on the wall, used it to put their hair up in rollers. And then-I guess this would have been in the late forties-3M began to observe what these consumers were doing, and their staff started rethinking the product in light of what they were getting back."

He then goes on to talk about what he calls the "backtalk cycle".

Well, worth a read:

http://hci.stanford.edu/bds/9-schon.html

Thanks, Richard, that's a great 3M story and one I'd not come across before.