There's a separate public/private keypair for every bitcoin address. You don't have a single private key that unlocks everything. Bitcoin addresses are a 160-bit hash of the public key, everything else in the system is 256-bit. - [Re: Bitcoin Address Collisions](/docs/forum/bitcoin-forum/65)
Bitcoins are sent to and from bitcoin addresses, which are essentially random numbers with no identifying information. - [Re: Repost: How anonymous are bitcoins?](/docs/forum/bitcoin-forum/7)