Satoshi made a judgement at one time that 1 MB was an appropriate limit based on that vulnerability, considering the state of the technology, storage, propagation, etc.. What is the evidence for that vulnerability being sufficiently smaller now or in the near future that a 8x or 20x or 1000x is appropriate instead?
The evidence is the 3.5 billion market cap as compared to 0 back then (or the most optimistic estimate maybe 5M). The network can support a LOT more "spam" today and still be considered valuable and useful by its users.
And also experience has shown us that there is not much spam. If there was, blocks would be 100% full all the time. When we switch to 8, 20 MB or whatever blocks, its going to be much ado about nothing. If the network was going to use that bandwidth right away, it would be using the full 1MB now.
And unlike the case of email, blockchain spam is not even read by human beings so the inconvenience to the network per message is very small (esp. when pruning, etc starts). You are trading the promise of a worldwide currency against the fear that some people might issue some frivolous txns! Bitcoin is unlikely to stay at its current adoption level. It is in a grow or die situation.
Someday there WILL be a fee market. When there are 100x more users and 1000x more txns.
