Like in any battle understanding your enemy is an important step in defeating them. On another note, it seems that security is to be stepped up at London tube stations.
http://yro.slashdot.org/article.pl?s...id=158&tid=126
I don't think it's an effective implementation, I think the government just wants to be seen as doing something. It will, however, appease the fear of people using the tube and limit the liklehood of further attacks in the trains.