In a Peer to Peer Electronic Cash system a 7 years history of the data sound quite sufficient. Keeping old sometimes worthless information comes with downsides.
I see the following benefits:
Downsides left to commenters.
“Sufficient” and “worthless” seem a bit subjective.
I assume that the peer-to-peer electronic cash system we want to build intends to be global, the foundation upon which a planetary civilization could build its economy. As such, it may involve many users, and despite some fundamental and common use cases, that global character will lead to a potentially wide range of possible use cases.
Some of those use cases may require a continuous and immutable ledger since genesis block. So I wouldn’t rush on discarding any part of the ledger.
Pruning methods already exist in Bitcoin Cash and are of everyday use in several upstream and downstream applications. But pruning the whole network discarding part of our history, doesn’t seem the way to go.
Ledger is the law.
If disk space and slow search are the problems, I would suggest exploring better methods for storing information and faster search engines.
This is a non-starter. Arbitrarily introducing new rules to confiscate and burn someone else’s money is a quick way to undermine confidence in the currency.
Burning lost money that has no benefit anyone anymore. People who still have access to the funds can just move it once every 7 years.
I think this proposal helps against using the block chain for storage. If someone cares to keep something in the P2P system they can send the minimum dust required.
Let us say I’ve an account on memo.cash and I would like to keep all my posts. I send the minimum dust to related address so it stays there for another 7 years.
You are suggesting an extreme overkill solution to combat a problem I don’t think is really a problem at all.
That would not work that way, memo data would not be kept by the majority of the nodes anyway, regardless of what you do.
I doubt this is something we’ll want to consider in the next 50 years, but just for academic interest, this has been investigated before:
Sakura, long term UTXO recycling mechanism for Bitcoin:
Abstract: The very long term viability, centuries ahead, of Bitcoin depends on preventing the runaway growth of the UTXO set (unspent transaction outputs). Also, the ever shrinking monetary mass of Bitcoin is a complication which hinders economic agents from fully relying on perfectly predictable monetary conditions. Here, we propose Sakura, a long term recycling mechanism to prune “dead” UTXO entries, defined as entries that have remained untouched for 80 years (defined as 4,200,000 blocks). It allows those “dead” entries to re-enter the pool of mining rewards, on top of the normal halving mechanism which normally occurs every 210,000 blocks. Sakura comes with a trigger condition that “dead” UTXO entries should represent more than 50% of the UTXO set. This condition prevents a premature activation of the change of consensus if there is not enough economic gains to justify the change. Sakura proposes an exponential decay mechanism associated to a half-period of roughly 20 years. The paper also presents a discussion to justify why those seemingly arbitrary choices are made.
It proposes a much longer “recycling period” (80 years).
My fundamental challenge would be: this assumes many entities will continue willingly wasting money by leaving unused UTXOs around. I’ll be surprised if in 20 years UTXOs are so easily lost as they were in Bitcoin’s early years. If software continues improving, I think it’s more likely that the future has fewer “dead UTXOs” than today.
If my great-grandchildren find I was wrong on this prediction, maybe that would be a good time to introduce a recycling mechanism for the long-term. 
Really interesting idea (Sakura proposal). I like the architectural drivers stated thus far. Will definitely read the paper itself and review. The thought of wiping out stale UTXOs goes against the core concept of stable reliable store of value. Weighted against the very real loss of units, it becomes an interesting thought experiment but nothing that needs a near term solution or justifies a priority above many other things. Done wrong it completely obliterates the key constructs of BCH and brings the house down around it. Tread super carefully on this one.
One very real potential scenario that causes me concern about ANY such idea - a LOT of BTC was lost in the early days (some of mine as well as machines were reset without backups cause it just wasn’t worth anything in real life, right!). The powerful concept of the BTC/BCH/Gold Standard is the absolute predictability of the total supply. It’s what allowed long term investment horizons and quite literally kicked off the funding of an empire where the sun never set. The first time such a mechanism comes up to kick in - the potential new supply of BCH that would be introduced is going to be fairly significant. Presumably there’s some rate limiting aspect to reduce this impact. But what’s going to not be predictable is how much of this old value will suddenly be moved right before it’s recaptured. THAT number can’t be rate-limited and would likely stress the markets should it occur. A counter argument to this is “well those coins could be moved at any time since they’re actually live and this would just force their hand and reveal the truth of the total currently available supply” - which perhaps is a short term pain that is a long term good thing. There’s a lot to consider and good arguments on both sides but the first few times this kicks in it’s going to be a Big Deal ™.
Well that wasn’t useful. If you need scaling you don’t want people to spend weeks downloading and indexing tons and tons of worthless data.
As the only data required to actually run a BCH node is pretty much the UTXO set, I don’t think it’s necessary, nor desirable, to try to do something like this (particularly at the consensus layer).
The initial syncing can be difficult - but I think UTXO commitments would be a far better solution (even if it is somewhat “trustful” initially).
I remember reading a write-up on this (by @tom I think?) a year or more ago that suggested committing the UTXO hash for -100 blocks from the current block (or something like that) which I thought was a pretty good idea.
I’m adding my “No, bad idea, don’t interfere with peoples’ money at rest” to the global consensus you will need to build for such a scheme.
Your proposal is extremely poorly motivated at this stage. No data, no numbers, no attempt to address the downsides for yourself, showing you have not followed previous conversation around this topic over the years. You will need to build a much stronger case for something that is currently not viewed as a future problem - or even a good idea - by many in the BCH community (as you can see from replies).
Thanks @freetrader. It wasn’t a proposal but it was an idea for discussion. I don’t have the expertise to create full technical proposal. However I see downside of having outdated data being downloaded and processed by hundred of people trying to build on the network. Specially with SLP data.
Yeah, as a “proposal” is a non starter and as an idea it is beyond stupid.
I apologize for being blunt, but this is not going to happen at any point, sorry to destroy your “creativity” or hopes for the future.
To say it differently: if anything from this “proposal” made it into Bitcoin Cash, it could no longer be called Bitcoin Cash, I would leave it for other project or fork it off myself and burn all bridges behind me with fire, desperado-style.
Please form better thought over “proposals” or “ideas” in the future, I expect improvement.
For all the people who do not realize what might be happening here, please study the concept of Overton Window.
The first stage is talking about an “issue” and even criticizing it, bringing it into public opinion.