On Fri, Aug 7, 2015 at 4:57 PM, Gavin Andresen via bitcoin-dev <bitcoin-dev@lists.linuxfoundation.org> wrote:
Every once in a while the network will get lucky and we'll find six blocks in ten minutes. If you are deciding what transaction fee to put on your transaction, and you're willing to wait until that six-blocks-in-ten-minutes once-a-week event, submit your transaction with a low fee.

All the higher-fee transactions waiting to be confirmed will get confirmed in the first five blocks and, if miners don't have any floor on the fee they'll accept (they will, but lets pretend they won't) then your very-low-fee transaction will get confirmed.

In the limit, that logic becomes "wait an infinite amount of time, pay zero fee."

That's only the case when the actual rate of transactions with a non-zero fee is below what fits in blocks. If the total production rate is higher, even without configured floor by miners, a free transaction won't ever be mined, as there will always be some backlog of non-free transaction. Not saying that this is a likely outcome - it would inevitably mean that people are creating transactions without any guarantee that they'll be mined, which may not be what anyone is interested in. But perhaps there is some "use" for ultra-low-priority unreliable transactions (... despite DoS attacks).

So... I have no idea what the 'market minimum fee' will be, because I have no idea how long people will be willing to wait, how many times they'll be willing to retransmit a low-fee transaction that gets evicted from memory-limited memory pools, or how much memory miners will be willing to dedicate to storing transactions that won't confirm for a long time because they're waiting for a flurry of blocks to be found.

Fair enough, I don't think anyone knows.

I guess my question (and perhaps that's what Jorge is after): do you feel that blocks should be increased in response to (or for fear of) such a scenario. And if so, if that is a reason for increase now, won't it be a reason for an increase later as well? It is my impression that your answer is yes, that this is why you want to increase the block size quickly and significantly, but correct me if I'm wrong.

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Pieter