Ethereum (ETH) price, performance and general information

Hey!

We've just launched our "No Loss Lottery" aka "Prize Linked Savings Account" built on Ethereum with Dai! It's been audited by Quanstamp and you can check it out below: https://www.pooltogether.us/

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Basically you buy a ticket for a chance to win and if you don't win you get all your money back. This is possible because the prize is funded by the interest earned on all the money used to purchase tickets!

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Would love feedback! Here is our launch blog: https://medium.com/pooltogether/introducing-pooltogether-2f80c7c0bfc6?postPublishedType=repub

http://www.ethdocs.org/en/latest/ethereum-clients/cpp-ethereum/

I understand the basic premise that the blockchain acts as a public ledger and tamper-resistant “proof”. If I want to prove to the world that I exchanged Widget A to John in exchange for $10, and that he actually received the widget, we can do so using a smart contract.

What’s stopping me from claiming I sold it to him for $10 and then accepting an additional $5 from him “off-chain”, i.e. on Venmo? The world won’t know that I earned 50% more on the transaction. I get that the same problem exists in non-blockchain contracts and transactions, but does blockchain or Ethereum solve for this in any way?