Rails and Bitcoin Wallets - Secure Architecture?

[orbital_velocity]

Howdy,

I'm in the planning stages for a Rails app that would:

• Allow users to carry a BTC/Litecoin balance
• Make purchases with their balance or an external wallet
• Transfer their balance to an external address

...among other things. My question is related to server architecture - should I run bitcoind locally, or on another, more locked-down server? If anyone has any experience with running a bitcoin wallet built on Rails, your input would be greatly appreciated.