if an address could create new, temporary, private keys, that might be smart
and if these new keys could have different rules and regulations. for example, one key might have an upper-limit on how much payments it can authorise, like, maybe 0.1BTC/month
and other forms of rules. like, "this private key can only send money to this address"
these keys can then be given to third parties, and this could automate stuff
and a new key can be deleted at any time. and the rules for it could be changed at any time.
they could be called 'third-party keys'http://bitcoin.stackexchange.com/questions/37822/dual-sig-wallet-with-upper-limit-on-one-of-the-keys-for-basicincome-co
being able to authorise third parties, but in a safe and controlled setting, would help my development with Basicincome.co, and I can imagine more potential applications, such as BitTip/CoinAwesome, subscription payments, auto-billing.