I've read some of the linked discussions, and it seems some of the participants fail to understand the basic economic theory of the marginal cost. In any high fixed-capital business, the net present value (NPV) determines the ROI (IRR) and determines the opportunity cost where investors apply their capital. Thus, in normal functioning markets, the lowest marginal cost provider does not expand their capacity to take all of the volume at their cost, rather the market price is set by the highest marginal cost provider and the lower marginal cost sell at that price to maximize ROI and thus investment. Realize that not all investors have the same opportunity cost (some have better competing opportunities than others), thus the supply of investors at any given ROI is finite.

However there is a risk. The fundamental change facing Bitcoin's future is the shift from a forced highest marginal cost price structure— because all miners get the same price for mining a block— to a free market transaction fee pricing structure where dumping or subsidies could be used to destroy the higher marginal cost miners and gain a monopoly, thus also compromising the security of the system. However, a monopoly strategy could be applied in the current Bitcoin by dumping or subsidy to force difficulty rates up thus destroying higher marginal cost miners, and/or simply being a greater proportion of the total system hash computing power.

A solution to this problem is simple and is necessary for another reason. A market-based transaction fee does not guarantee any level of hash computing power, unless the user is motivated to pay more for more security and/or transaction processing speed. Either this is incentivized by having the recipient pay the transaction fee (which is a good idea any way), or the transaction fee should be set globally by the system to maintain a desired level of hash computing power (which means transactions that don't need it are penalized but at least it is consistent). Thinking through this further, market-based fee even if incentivized as stated, may not guarantee enough profitable business to offset the determined monopoly strategy, thus a global system transaction fee is safer.

However, a sufficiently subsidized monopoly strategy can still drive the difficulty up and/or capture a larger proportion of total hash computing power.

One potential counter-measure is LiteCoin's Scrypt, as it should make it more expensive to monopolize and reward more CPUs to be miners thus decentralizing stake, although it does open the botnet risk. If debasement is paid back to users by encouraging them to run full nodes and leveling the playing field between ASICS and CPUs using Scrypt, then it is the world's processing power versus the monopolist. The user who is not gaining from mining and thinks they are running a full node, could be advised to run a test for presence of a botnet. This plays well with my conceptualization that perpetual debasement is necessary (of which some might disagree so this answer is not making that claim). Btw, I think Proof-of-Stake moves in the opposite direction by centralizing stake.

A potential means for someone without deep pockets to monopolize Bitcoin, would be if ever there was a way to borrow sufficient Bitcoin to purchase the necessary 51% computing power, then destroy Bitcoin forcing an inflationary spiral as holders stampede to sell out, then repaying the borrowed Bitcoin at a fractional of the original value.

The current block size transaction limit doesn't accomplish anything other than cap throughput, because it doesn't move even if hashing capacity expands by either of the simple mechanisms in the prior paragraph.

Given my prior two answers got negative votes, I am also expecting this answer to fly over the heads of some voters. Apparently some of the participants either don't have a very good grasp of economics (or have a vested interest or I am wrong and they didn't comment to tell me why). I would appreciate if downvoters would at least try to defend their logic with a comment below my answer. That gives me an opportunity to debate them and show them why I think they are wrong (or to admit my mistake). The point is to make sure we collectively have the correct logic.