[kang]

Blockchains allow transfer of value even between parties without contracts or deals or even trust, by exchange of a rare token. For eg Cars from different companies may negotiate among themselves using bitcoin, this was never possible earlier because for cars to exchange tokens theyd have to be under some central authority or some contract. Bitcoin provides the ability for signing contracts on the fly.. Another eg would be a car stuck somewhere opens a rescue request on a website. An automated crane bids and goes and rescues the car and goes away taking the bitcoins. For this to exist today some deal is needed beforehand.

[marxidad]

Could this be done with Ethereum <http://www.ethereum.org/ >?

[kang]

It can be done with any blockchain; anything that is anonymously trade-able in public.