So basically you guys are saying that those with enough money to open an ASIC farm, and those who live in places with very low electricity costs, will be able to make money mining. OK, but doesn't that confirm my point that mining is a useless waste of time and effort for the rest of us?
Yes. Mining is a competitive business. As such, it will only be profitable for those who have access to the most affordable necessary resources. Others may mine at a loss as a hobby, but as a source of income it will be a waste of time and effort to those who don't ahve access to competitively priced resources.
I am persuaded that the rise of Bitcoin was mostly due to a large network of smalltime users running the full Bitcoin software and generating coins, and I am afraid that there is no incentive anymore.
There are many incentives for bitcoin use beyond mining for cheap profits. The fact that it is an electronic form of payment with no counter-party risk is a huge incentive for merchants. The fact that you can create backups of your money is an incentive for users. There are several other incentives as well.
As far as the other argument is concerned - that once the Bitcoin economy is huge there will be enough of an incentive to maintain the network even if the transactions fee remain low - I think that's plausible, but we must get there first, and how do we get there if the system collapses for lack of individual maintainers?
It won't collapse. If total global hashing power is reduced then the difficulty will be reduced which will result in mining becoming more profitable for others. As profits increase, more people will start mining again which will result in difficulty increasing again. Eventually a mining equilibrium will be reached.