Importing Private Keys

[WuLabsWuTecH]

I'm trying to move my wallet from one platform (blockchain.info) to another (bitcoin qt).  If I import a private key to the new platform, what happens to the old one?  Do I have to do something to tell blockchain.info that I'm no longer using that service?  Or does it just somehow know that it's been "fired"?

[mjc]

The keys are only used i the wallet itself.  The block chain knows nothing about where the keys lives and doesn't care.  As an example if an attacker were to obtain your keys and import them then they would have access to the Bitcoins in that address.  this is why care needs to be taken to protect the private keys.