All well and good sir gmaxwell, If I may suggest the issues is the ability to redirect funds in this way makes StongCoin and Blockchain.info fundamentally compromised
I believe that blockchain works in a different way then strongcoin.
If you use the browser extension I believe you are relatively safe from arbitrary code changes like the one we witnessed at StrongCoin.
Next step in security is probably to have an hardware wallet with the private key that can sign the transaction without ever letting the computer see the private key.