I had also written else where:
The reputation/rank aspect is just proof-of-stake in transactions. It has the same properties of proof-of-stake wherein your stake determines how much rank you realistically have (and not just lose it all to transaction fees).
Also since it requires the transaction graph, then it is incompatible with privacy and anonymity.
I don't understand why everyone is so excited about NEM. It is just a rehash of PoS. Where is the innovation?