Someone else on that site responds with an interesting counteropinion:
Second, for Bitcoin to have real world effects, it must cross into the physical somewhere and this is where traditional intelligence gathering, law enforcement and customs will continue to play a key role. Just as drugs are seized where some other currency is used, so too will drugs and weapons be seized if Bitcoin is used. Australian police have already made arrests where Bitcoin was used and the market place was on the anonymous TOR network.
Bitcoin poses challenges that need to be addressed but it may not be the game changer that the author implies.
from http://www.lowyinterpreter.org/post/2012/11/16/Reader-riposte-Bitcoin-and-terrorism.aspx