Contract Rollout

Contracts should have a substantial and prolonged testing period - before substantial money is put at risk.

At minimum, you should:

• Have a full test suite with 100% test coverage (or close to it)
• Deploy on your own testnet
• Deploy on the public testnet with substantial testing and bug bounties
• Exhaustive testing should allow various players to interact with the contract at volume
• Deploy on the mainnet in beta, with limits to the amount at risk

Automatic Deprecation

During testing, you can force an automatic deprecation by preventing any actions, after a certain time period. For example, an alpha contract may work for several weeks and then automatically shut down all actions, except for the final withdrawal.

modifier isActive() {
    if (block.number > SOME_BLOCK_NUMBER) {
        throw;
    }
    _;
}

function deposit() public
isActive() {
    // some code
}

function withdraw() public {
    // some code
}

Restrict amount of Ether per user/contract

In the early stages, you can restrict the amount of Ether for any user (or for the entire contract) - reducing the risk.