adam3us

We've been incredibly fortunate in that our investors understand open source efforts and appreciate the importance of working within the context of a technical standards-based community. We'll have more to say about our group of investors in the coming weeks, and many of them will be weighing in personally on questions like this. As co-founders of Blockstream, we firmly stand behind bitcoin and blockchain technology and the values embodied in its code, including decentralized, open, permissionless and trustless innovation.

yes you can have a side-chain recursively off a sidechain, and there can be reasons to do that.

i'm waiting for the zerocash sidechain :)

yes actually I was operating an anonymous remailer at the time and hashcash was to throttle spam in anonymous networks because you cant ideally rely on identity there. there were a number of applications of hashcash. http://hashcash.org/papers/hashcash.pdf

bitcoin also is independent from identity, so there is a common theme there. see also b-money http://www.weidai.com/bmoney.txt by Wei Dai and bit-gold by Nick Szabo two ecash ideas that predate bitcoin that propose to use hashcash mining. also Hal Finney's RPOW also uses hashcash mining.

Not really in competition, they are different concepts treechains are a scaling idea by petertodd. It would be convenient to experiment with treechains on a sidechain as sidechains are generic extension mechanism with significant flexibility in the rules that can be used on a sidechain.

For example zerocash could be implemented on a sidechain or other things that have radically different formats and ownership tracking mechanisms.