Coinbase didn't sign this letter because I think the intention behind it is wrong.
On the surface it is a communication about how exchanges would handle the hard fork, and a request to BU for replay attack protection. But my concern was that it was actually a thinly veiled attempt to keep the BTC moniker pegged to core software. I think a number of people who put their name on it didn't realize this.
A couple thoughts:
- Certainly it makes sense to list forked assets separately on exchanges, especially during periods of uncertainty. But it doesn't make sense to say BTC can only be modified by one development team. If there is overwhelming support from miners and users around any new version of the software (regardless of who wrote it), then I think that will be called Bitcoin (or BTC).
- The replay attacks are a real concern. We spent some time talking with Peter Rizun from BU last week and he/they seem very open to hearing ideas on replay attack protection and coming up with solutions, which was great to see. It is not as trivial for them to add as I originally thought, because it seems adding replay protection would break SPV clients (which includes a number of mobile wallets). We as a community could probably use more brainstorming on how to solve this generally (for any hard fork). I'll make a separate post on that.
- I think regardless of what was stated in the letter (and people's personal views), pretty much every exchange would list whatever version got the overwhelming majority of miner and user support as BTC. I also think miners know this.
- A number of exchanges (GDAX, Poloniex, Gemini) didn't sign the letter, or later clarified their position on it (ShapeShift, Kraken), so I think there are a variety of opinions out there.
- I think creating public industry letters that people sign is a bad idea. They haven't been very effective in the past, they are "design by committee", people inevitably say their views were not accurately represented after the fact, and they tend to create more drama. I'd rather see private communication happen to move the industry forward (preferably on the phone, or in person – written communication is too easy to misinterpret people's tone). Or to have each exchange state their own opinion.
- My goal is to have Coinbase be neutral in this debate. I think SegWit, BU, or other solutions could all be made to work in bitcoin. We're here to provide whatever our customers want as best we can across all digital currencies, and work with the wider community to make forward progress.