I was looking into Ripple last night, and it uses something similar[1]: you enter a set of nodes that you trust will not collude together, and an 80% supermajority of those trusted validators propose transactions, and then an 80% supermajority of all nodes on the network accept those transactions for a new consensus.

It's a lot more efficient than Bitcoin (no proof of work, it's just another consensus protocol), but the trade off is that 1) it doesn't have all the feel-good rampant libertarianism of completely untrusted decentralized consensus of Bitcoin 2) you have to pick a good set of trusted nodes and trust them all not to collude

(Ripple has other problems that skeeve me out, but after thinking about it federated consensus isn't one of them. I think a lot of altcoins are using federation, actually...)

[1]: https://ripple.com/build/xrp-ledger-consensus-process/#the-x...