To add to that, the escalating hashrate war within Bitcoin between Unlimited and Core is popcorn worthy.

And within the wider space of blockchains, improving access to strong anonymization techniques appears to be moving forward quickly: https://blog.ethereum.org/2017/01/19/update-integrating-zcas...

What's the unlimited thing?

It has to do with the need for increased block sizes. Right now, each block (chunk of validated transactions) can only be 1MB in size. This restricts the total throughput of the network, but keeps the total size of the blockchain down and the growth rate low.

The original expectation was to gradually increase the block size to increase capacity as more users joined the network, eventually transitioning most users to "thin" clients that don't store the (eventually enormous) complete blockchain.

The Core devs right now feel that the current situation (every node a full peer with the complete chain, but maxed out capacity and limited throughput) is preferable for a number of reasons including decentralization, while the Unlimited devs feel that it's time to increase the block size in order to increase capacity and get more users on the network, among other things.

Decisions like this are usually decided by the miner network reaching consensus, with votes counted through hashing power/mined blocks. I'm not sure where things stand at the moment, but it's been interesting to observe.

I understand it's become a rather contentious topic in the community.

Thanks for the great explanation! So where does segwit come into this?

I'm not the best person to ask, and I don't fully understand segwit, but I think it's the Core devs (partial) solution to the problem of scaling up the network without increasing block size.

IIUC, segwit makes certain kinds of complicated transactions easier to handle (ones with lots of inputs/outputs), possibly allowing more transactions to fit in less space, and lays useful groundwork for overlay networks like Lightning. I think the thinking is that overlay networks can be fast, and eventualy reconcile against the slower bitcoin network.

Unlimited would rather just scale up the bitcoin network in place, instead of relying on an overlay network.

You'd probably get better information from bitcoincore.org and bitcoinunlimited.info, or the subreddits /r/bitcoin and /r/btc (for core and unlimited, respectively, they split after moderator shenanigans in /r/bitcoin).