Your clarifications are fine, but I do find it to be a bit of an uncharitable reading of what I wrote, because it seems to be far less wrong than you make it out to be, if we're to believe wasoxygen.

You're effectively saying that since someone partially disagrees with me I'm rude. This is how we got into trouble last time - I can't stop you from being personally upset by the things I say but I can remind you that the excessive length and care you get in my responses are a sign I'm trying not to piss you off.

wasoxygen is wrong. Blockchains are distributed ledgers. The distribution is the point. BitCOIN was derived from BitTORRENT where the entire point is the distribution and decentralization. The difference between bitcoin and bittorrent is there need be no central server to point new users to the blocks because there are no blocks. Everyone has the whole thing or they aren't a part of the equation. If you aren't 100% identical to everyone else on the network you aren't on the network.

Instead of saying a blockchain is a glorified database, maybe it's more accurate to say it's a database with an elaborate checksum?

It's not a database. It's unwieldy and impossible to manipulate. A blockchain is an indelible, unfalsifiable, permanent record of transactions. You're absolutely right: if you write "2 plus 2 equals 5" in the blockchain, it will say that two plus two equals five. however, that block will have a unique identifier and the user that wrote that on the blockchain is also indelibly marked. And you're absolutely right that the blockchain is only as good as the information on it. But again, if you write something wrong or dishonest, you have written it forever, out where it can never be edited. Mistakes will be made because we're people but a pattern of "mistakes" is either incompetence or malfeasance and now that it's there forever, anyone can investigate. More importantly, there is no horizon beyond which mistakes cannot be found.

- The security increases with the number of copies of the block chain out there, but since you need the entire chain to be copied it can be extremely storage intensive.

No. With a public blockchain the durability increases with the number of copies. A 51% attack on an authentication blockchain would create two blockchains. Any transaction that happened before the 51% attack would be on both blockchains while any transaction that happened after the 51% attack would only be on one. if KBChain made the mistake of letting anybody on board, and got 51%attacked, KBChain Classic would release a memo saying "well that was dumb, we've still got your original verification and we're making our admissions standards more stringent." The data itself remains inviolate.

- Keeping all of these copies in sync costs a lot in terms of data traffic, which also creates latency. In fact, all the hashing, even if it's not quite as bad as I thought, will create latency as well.

Yes. But latency doesn't matter in the slightest when we're talking about authentication. If I'm buying and you're selling the money is going into an escrow account that you won't see for a month anyway so who cares.

I think it's safe to say it's not "effectively zero cost", but it could be an acceptable cost for some applications. I also think it's safe to say there are many applications it would not be a good fit for.

Thus once again we move from "I don't understand it and you're wrong" to "I understand it a little better but you're still wrong." A blockchain need not have 8,000 members. You don't get to play with Hyperledger unless you have a board of directors. Authentication on Bitcoin is dumb and authentication on the Ethereum mainnet is tortuous but authentication on an Ethereum-compliant private net could be fast as networking. Arianee, for example, accomplishes its mission perfectly if they just assign a node to every vendor that wants their products verified. If you've got 100 brands you've got 100 nodes and the network is secure because the only people who can write to the network are the brands that depend on it.

That's 100 Raspberry Pis or the equivalent. Give each of 'em a 1TB hard drive. You're talking about a $500 cost for companies that don't sell watches for less than $5k ea. Breitling did 530m CHF in sales last year. I would say "effectively zero" is an accurate description.