Other than the spam attack average block size at around 0.4 MB. Absolutely no where near full blocks
If you look at the last 2 years you will see that
the daily average it has doubled in the last 12 months. Even if the growth is linear rather than exponential, if it continues at that pace it will be 0.60 MB/block by mid-2016.
On the other hand, the stress tests showed that the actual capacity of the network is only 0.75 MB/block. And since traffic is not uniform over the day and over the week, there will start to be recurrent "traffic jams" well before the traffic reaches capacity; maybe as soon as mid-2016.
Moreover, a "spam attack" now is very cheap because the attacker only needs to generate more than the average free capacity, that is 0.35 MB/block, to create a permanent traffic jam. By mid-2016, he will need only 0.15 MB/block.
The Blockstream devs know this, for sure. Why don't they care?
let alone blocks 18 times bigger than the current.
The blocks will not get 18 times bigger with BIP101. The will continue to be 0.40 MB now, and will continue to grow at the same pace as they would with 1 MB limit. The effect of BIP101 will start to be felt only sometime in the first half of 2016, when traffic will get to 0.55 MB/block close to the 0.75 MB capacity. With the 1 MB limit, there would start to be recurrent jams and long waits; whereas, with the 8 MB limit, the traffic will just continue growing beyond that value, at its natural rate, and maybe reach 1 MB/block in 2017.
Most of the space is spam and dust anyway so even if we had full blocks the correct fee would get your transaction through no problem.
That is true. If a minimum fee of (say) 0.001 BTC = 0.20 USD was imposed on each transaction, the traffic would probably drop by 80% or more, and the block size limit would not be a pressing issue for a couple of years, at least. But neither camp wants to see hat, for several reasons...
