Quote from: Michael_S on March 02, 2013, 12:58:31 AM

So does this means that due to today's 1 MB limit per 10 min (i.e. per block), if the number of transactions get so large that more than 1 MB of transaction data is generated every 10 min, then some transactions will never ever make it into the blockchain, if their transaction fees are too low?

No. We will not hit today's limit today. As for the near future, I already stated:

Quote from: Yurock on March 01, 2013, 06:49:38 PM

Block size limit is artificial and will be adjusted as needed in the future.

Quote from: Michael_S on March 02, 2013, 12:58:31 AM

(2) The Bitcoin clients should get a feature to revert transactions that are not yet in the blockchain, because if I transfer 1 BTC to address xxx with a low fee yyy, and after some days or weeks my transaction still does not show up in the blockchain, then I might want to revert my transaction and try again with a higher fee zzz > yyy.

Yes. And also a way to add fees to existing transactions. AFAIK, it is already discussed by Bitcoin software developers, so we may see it implemented some time soon. Recipients of bitcoins will also be able to add to the fee.

Quote from: Michael_S on March 02, 2013, 12:58:31 AM

(3) As a result of this mechanism, there will be a real "fight" to get one's transaction into the blockchain

I would use the word "compete". Competition is an important market force, and Bitcoin is designed to be governed by market forces.

Quote from: Michael_S on March 02, 2013, 12:58:31 AM

so in practice this means that transactions will no longer cost "almost nothing"

Yes. Transactions cost something to the whole network. Every new transaction has to be propagated through the network and processed and stored (at least for some time) by every full node. Today, a large part of this cost is paid by newly generated coins, I think (but may be wrong). Let those who makes transactions (and thus supposedly needs them) pay most of this cost. Seems fair to me.

Quote from: Michael_S on March 02, 2013, 12:58:31 AM

transaction fees would soon become so high that for example micro-payments and small donations become prohibitive due to the high fees, and it would soon be cheaper again to use PayPal!

Bitcoin is clearly not going to be generally suitable for payments of few cents. Other than that, I think, fees will not be prohibiting. From charts on blockchain.info, I estimate the average today's fee to be below equivalent of 4 U.S. cents. Multiply it by 5, and it will still seem quite acceptable to me.

Quote from: Michael_S on March 02, 2013, 12:58:31 AM

(4) As a result of (3), people will move to make bitcoin payments more and more inside "closed sub-systems", i.e. bitcoin banks that do their own bookkeeping on their customers' accounts without loading the blockchain. For example there could be a MtGox subsystem or a blockchain.info subsystem, to name just two. When I transfer BTCs from my MtGox account to another person's MtGox account, I would not use the blockchain, but the MtGox internal bookkeeping would carry out the transaction, just like in today's banking system. This would avoid transaction fees, so people will favor this variant. But this also means that many benefits of bitcoin as we know it today would vanish, and the whole bitcoin system would move towards a de-facto centralized system that is again built on trust into a cartel of a few "subsystems" (bitcoin banks), and these sub-systems may even run fractional reserve banking without their customers knowing about this.

Remember, here you are talking only about micro-payments. Most people who need to transfer an amount like 10 BTC and up will not care to pay 0.01 BTC transaction fee. And fees are roughly per transaction, not per amount transferred. So, in the future, most micro-transactions are expected to be handled by other systems based on Bitcoin as a unit of value. As for larger transactions, Bitcoin is quite capable to handle them. So, only small (I think) part is going to move to systems that handle bitcoins indirectly. And it does not mean centralization. Cryptocurrencies of different kinds are being developed and launched, like Ripple and Open Transactions. They have no problem using Bitcoin as a unit of value. They may be more suitable for instant payments and micro-payments.

Quote from: Michael_S on March 02, 2013, 12:58:31 AM

Also, these sub-systems (bitcoin banks) would be vulnerable to government interference etc.

Like Bitcoin to fiat exchanges, they may be points of failure. But the possible influence is limited by at least two factors:

Only a part of the whole Bitcoin economy will see an influence. Larger amounts of bitcoins that reside in normal Bitcoin wallets will not be affected.
There will be no monopoly. If, for example, you close one large Bitcoin payment processor, others will catch up.

Quote from: Michael_S on March 02, 2013, 12:58:31 AM

solution to keep the bitcoin system open and avoid the outlined evolution towards closed sub-systems (="de-facto-bitcoin-banks") would really be to change the way that transactions are stored, as outlined in my last post

Your proposal has weak points, but the general idea is worthy, I think. The idea that since total Bitcoin supply is finite, amount of storage required to track every unit may also be finite and within capabilities of future systems.

Quote from: Michael_S on March 02, 2013, 12:58:31 AM

...Or am I missing some fundamental point here and all my worries are pointless?

There are surely things to worry about, and different solutions to the problems have to be considered.