Bitcoin Forum

NaN.

The document written by Gavin explains it all in detail.
https://gist.github.com/gavinandresen/4120476

tl;dr:

- The purpose of the messages is to allow bundling more information than just amount/address at payment time.
- It also allows a merchant to sign the payment request, ensuring that no one's modifying the request in transit.
- Nothing is stored on the blockchain.
- It identifies the receiver of funds (which you usually do know).
- It does not identify the payer.
- It can act as a receipt, and proof of payment, (because the merchant signed the request, the buyer has proof that a transaction was requested and so can prove they paid for goods).

Think of it as a newbie friendly alternative to just pasting an address in an email.

Also, it's fully optional, I don't think silk road will ever use it.

Let me know if you have more questions.

EDIT:

Mike Hearn talked about it recently too: https://bitcointalk.org/index.php?topic=262564.msg2807404#msg2807404

Where does this nonsense come from.  The burden of maintaining books is on the comapny.  Saying "sorry we can't issue receipts so we don't pay taxes" is stupid.  Sorry it just makes no fucking sense.  The IRS will say ok then since you can't prove your books, or show your revenue or expenses we are simply seizing EVERYTHING.  Companies maintain books so they can show the LIMIT of their revenue and profit and thus limit the amount of taxes they pay.

Of course even without a payment protocol companies are required to maintain books which can be audited.  It doesn't matter if you take payments in cash, gold bullion, pounds of marijuana, or Bitcoins.  The lack of a payment protocol doesn't make it impossible to issue a receipt, it makes it impossible to know that (as an example) when you are "sending coins to MtGox" that you are ACTUALLY sending coins to MtGox and not some hacker who infected your browser and changed the address you see on the screen with his address.

Simple version: The store chain 7-11 does tens of BILLIONS of dollars worth of sales in cash.  Do you think a lack of cryptographically secured payments suddenly makes their entire operation tax free.  Sorry Mr. IRS agent we erased our cash books so we can't show how much in sales or profits we had and thus are opting to not pay taxes.  Failure to keep accurate books means the IRS gets to estimate what revenue, profit, and taxes are owed and trust me they will be very "generous" in their estimates.

I mean does that even make logical sense to you?

The company could destroy the receipt as well.  It is called fake books and it predates Bitcoin by couple thousand years.