I like this project very much but I do not understand why there is only 12 witnesses. 7 people can very easily collude or get captured and then the network is basically dead. Why not more?
Cause otherwise nobody would have time to check and select seriously the witnesses, it's explained in whitepaper. Look at what is happening on Lisk or other DPoS coin, selection of delegates is a complete mess, nobody knows who is who anymore. Better have 12 reliable witnesses than hundred of randomly chosen ones.
And no, 7 people out of 12 can't easily collude and it's always possible for anybody running a full node to check if witnesses behave correctly.