Quote from: Qwedcxza1 on June 15, 2013, 12:46:21 PM

If the blockchain did contain information on other currency transactions then it might be possible to operate a derivatives market. Imagine if the Litecoin and bitcoin blockchains were combined and the proof of work was applied to both combined blockchains. We could then build an exchange and a derivatives market between litecoin and bitcoin. If fiat currencies became available in digital format we could just have one big blockchain for all financial transactions in whatever currency.

there is 'Merged Mining' http://mining.bitcoin.cz/what-is-namecoin

also, according to this- it is possible to trade across chains: https://en.bitcoin.it/wiki/Contracts#Example_5:_Trading_across_chains

the big blockchain clearing house is basically what Confidence Chains is all about: https://docs.google.com/file/d/0BwUFHE6KYsM0ZkxLVmFwbXQ3ck0/edit?usp=sharing