Ideal gap for maximum impact

Delhi blasts jolted me. The phone was engaged throughout while I was ensuring well being of my friends and also confirming same to my friends who are across the country (thanks to my company, I have had the opportunity to dwell at three states and presently my work take me to further two states).
I was caught unaware this time around when there was a second incidence of bomb blast at mehrauli road, not even a single call came to confirm my well being... I was looking for an answer.
In my opinion the gap which should be there between two blasts was too narrow that it could not muster enough impact. There is a clear problem visible in the misunderstanding of human behavior pattern. These terrorist are technical masterminds but they lack marketing skills. I guess this skillset is critically required. Let me reiterate this by some facts (sorry but will refer to history).
The most celebrated bomb blast incident was Bhagat Singh throwing bomb in parliament. it didn't had any shrapnel's but only loud sound. The first mover advantage! there was no historical incident i can recall where the bomb blast was conducted to express anguish. The first mover advantage is a great edge over other but it might not be possible every time.
Second most memorable bomb blast was the bombay (early 90s). The biggest ever! If I recollect correctly it had the maximum impact death toll across. When ever you enter a market as second player you must use technology to fullest.... banking industry is a witness to this (you might have got a clue , whom I'm talking about).
I'm skipping global incident of blasts. The latest trend of multiple blasts has a hint of repackaging. instead of one big blast which is technically difficult to execute they are relying on the multiple blasts. Also kindly note that the weekends are used. since out of fear, public at large are glued to Tv and see the blast clipping thus the required impact is achieved. The trend wave can even pull off the not so good products like ones used in surat to deliver the impact.
The latest failure (in terms of impact) will help them realise the lack of knowledge they have.

PS. i don't mean to hurt anyones' feeling but it is just a sarcastic smile at the traders of terrors...