Also keep in mind that your transaction is sent to *everyone*. This is great because it means that if you have your wallet.dat file with you, you could theoretically travel the 7 seas, hop off at the nearest port, walk up to the first best PC that is synced, update the wallet.dat file and start buy from whichever merchant you choose right there and then.
That's correct right?
That's about right.
It is also possible to "receive" bitcoin to an address that is paired with a private key that is stored on paper, having never been connected to the internet. When the time comes to spend to coins held on said address, the private key is imported into a Bitcoin client or redeemed through a reputable service, such as blockchain.info.