user1179: Is the sender's address the only way to identify the seller?
I don't see how this would work for a large websites that accept bitcoins. Since all of the transactions are visible, anyone can claim address x is theirs and that they sent the payment. 
I guess the only way would be to generate a new address for each transaction? Seems messy and hard to keep track of things.
Also, I though I'd add another question since I mentioned large websites. Would it be possible to automatically notify the server when a payment arrives? I'm talking about something like paypal's IPN system. So that everything would be automated. If the person buys a subscription for example, then upon payment confirmation it gets activated automatically.

user85: There is nothing messy or difficult to keep track of about generating a new address for each transaction. Generating an address is a very cheap operation and you can generate thousands of them in advance if you want. The way Bitcoin is designed, there is no different between using the same address for multiple transactions or using a new address for each transaction. It makes no difference to the system at all.
That said, I think the Bitcoin system should have permitted you to put an identifier in the transaction. 16-bits would have been sufficient.

1179: <p>Is the sender's address the only way to identify the seller?</p>

<p>I don't see how this would work for a large websites that accept bitcoins. Since all of the transactions are visible, anyone can claim address x is theirs and that they sent the payment. </p>

<p>I guess the only way would be to generate a new address for each transaction? Seems messy and hard to keep track of things.</p>

<p>Also, I though I'd add another question since I mentioned large websites. Would it be possible to automatically notify the server when a payment arrives? I'm talking about something like paypal's IPN system. So that everything would be automated. If the person buys a subscription for example, then upon payment confirmation it gets activated automatically.</p>
 85: <p>There is nothing messy or difficult to keep track of about generating a new address for each transaction. Generating an address is a very cheap operation and you can generate thousands of them in advance if you want. The way Bitcoin is designed, there is no different between using the same address for multiple transactions or using a new address for each transaction. It makes no difference to the system at all.</p>

<p>That said, I think the Bitcoin system should have permitted you to put an identifier in the transaction. 16-bits would have been sufficient.</p>
