Waves admin just banned NGR asset (niggercoin) from their "decentralised" exchange because it hurt someone's feelings. Not like I think it was great idea to promote such an asset on waves, yet it's not how this "decentralised" exchange supposed to work.
https://www.reddit.com/r/Wavesplatform/comments/6h15e5/waves_not_decentralised/
http://boards.4chan.org/biz/thread/2428429/wave-platform-cuts-ties-to-nigger-coins

Since waves claim they made "decentralised permissionless exchange" I think we can call it scam for now. Some people who "misbehave" will loose their money now.
It seems WAVES admins have full control over their exchange and can censor everything they want.

[WITNESSES]

Minig pools are witnesses. Miners are voting for these witnesses. There can't be more than some 10-20 active mining pools, or these pools would depend on luck heavily.  Limited blocks can be solved in a hour, so if 100 minig pools would compete for these blocks no predictable output can be calculated.
So users would stick to very limited number of top mining pools with predictable stable value output.
Minig pools form very limited, by protocol, number of witnesses. Bitcoin is a DELEGATED Proof of Work coin. And witnesses in full control of bitcoin, and miners with their hashing power now choose BU or BS WITNESSES to vote on a future improvements and transaction processing rules.
There is no and can't be, by Bitcoin protocol, any real decentralisation.

Which coins can do instant confirmed transactions? As far as I know it's Dash, Byteball can do it too due to fast confirmations by witnesses. Probably some DPOS coins can process instant transactions too, does anyone know some?

As far as I know, if coin use less time to generate block more orphaned blocks will appear in this coin.
The thing I don't understand is how orphaned blocks affect network. For example, if PoS coin have very low block time, some 5 - 10 seconds, it will lead to massive generation of orphaned blocks. Why this is a problem? Do orphaned blocks flood the network with additional data? Do they somehow responsible for  blockchain bloating? Do they delay block generation? If orphaned blocks only affect miners, why should average users care?