imo, this comment needs more visibility, it is about the real usecase for RBF
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The cashier says excuse me sir you have paid with an RBF transaction and we do not accept RBF transactions.
OK says the man refund me and I'll pay with cash. Sorry says the cashier but I can not refund you. You'll have to send another transaction but make it non-RBF and then send another transaction to bump up the fee on the first transaction and change the destination to yourself thus refunding yourself.
How do I do that says the man shaking his head in disbelief. Well says the cashier it depends on which wallet you are using and as I am not familiar with your wallet I can't really help you.
I'll just pay in cash says the man this bitcoin stuff is just to complicated. The cashier says OK but your first transaction will go through as well if you don't bump the fee and change the outputs. So if it is going to go through says the man why don't you just accept it.
Well says the cashier if I did that you could leave the shop and then do a double spend and the boss would be mad at me because we would lose out. I have another idea though, you could wait for the transaction to confirm in 10 minutes or so and then I can accept it because it will be too late by then for you to so a double spend.
OK says the man, this is crazy but I'll wait 10 minutes to keep the peace.
Ten minutes pass . . . . . . .
OK, says the man, I am going now. Sorry sir, says the cashier but your transaction has not confirmed yet. Because bitcoin is limited in how many transactions can fit in a block, you transaction did not make it this time. You will have to wait another 10 minutes.
Look, says the man, I have played this game enough I have to go now. OK says the cashier but you need to pay me in cash. If you come back later I'll check to see if your transaction has confirmed and I will refund you.
F*&&# hell says the man. This bitcoin shit is really weird and f'd up. You can be sure I won't be using it again.
Man exits and tells all his friends that unless they are computer scientist with hours of free time they should forget about bitcoin.
Cashier talks to boss and tells him another pissed off customer just abused her over bitcoin and asks why the hell they accept this crappy payment method that no one can understands and which pisses off their customers.
Boss says OK then we will stop accepting it, I don't need more strife in my life.
Rinse and repeat enough times and we will never have to increase the blocksize because nobody will be using bitcoin.
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https://www.reddit.com/r/Bitcoin/comments/3zju81/rbf_optin_a_man_walk_in_a_bar_order_a_coffe_drink/