I agree, and said earlier, that 9/11 was a game changer and a "where were you when" moment. I could bore you with a great deal of detail about what I did and thought that afternoon. 7/7 was rather different.
A hundred times as many people died in the Asian tsunami. My point is that that event is way more significant in the tragedy stakes but has been pretty much forgotten while 9/11 goes on and on. If you want to commemorate tragedies shouldn't you go for the tsunami first?