This is something very new to Bombay - gunfire and bombs happen all the time in Kashmir, but not in Bombay, and there is definitely no attack of such public places. Those terrorists have (had?) a death wish - there is no other explanation. There was no chance of escape, given just 30-40 terrorists in a city of millions. So they are trying to become martyrs, taking as many innocent lives as they can.
[A little while after 9-11, some terrorists drove into the Parliament complex shooting at random. The press in India started calling that 12-13 (Dec 13, the day of the attack), iirc. But that was nothing - comparatively.]
People in India are pretty riled up, and quite likely a similar reaction as Americans had to 9-11. Kill the terrorists (some idiot politician or cop has already used the dead-or-alive theme), use strong anti-terror laws (previous PATRIOT-like laws TADA and POTA were allowed to lapse with a refusal to invoke such laws as late as last week), etc. It's easy enough to blame Islamic extremists for this tragedy, and very likely they are. Things are just going to get a lot worse now...
Why now - recently, some right-wing Hindu extremists bombed a Muslim-majority locality. (This apparently followed many other incidents perpetrated by Islamic terrorists.) Anyway, this is similar to (connecting to my memory-map) what happened in 1992-93:
Dec 6, 1992: Hindu right-wing mob destroys the Babri Masjid.
Jan '93 - Hindu-Muslim riots break-out, especially severe in Mumbai. [The area around my college is among the ones put under curfew.] Many casualties among Muslims, with allegations (probably true) of Hindu-police complicity (at the very least, inaction by the police as Muslims were killed).
March '93: Serial bomb-blasts at 7? sites across Bombay, within minutes of each other. Over 300 killed iirc.
So there's a pattern...
Update 12/2: Amitav Ghosh opines in the NYT that this is not exactly India's 9-11. Ghosh makes a good point that America was not used to terrorist attacks on American soil unlike India, which has a much longer experience with terrorism (though he offers an example of the 1984 anti-Sikh riots - but America is used to communal/racist riots). He also says 9-11 refers not just to the attack itself, but the "utterly misconceived military and judicial response" that followed. I must disagree with Ghosh to some extent here - I think the US invasion of the Taliban-ruled Afghanistan was right, even as the excesses at Gitmo and Abu Ghraib were wrong.
I look at last week's events as India's 9-11, as the day the Indian government and the world community (read the US and Pakistan) realize these terrorist activities cannot continue, and action is taken by all concerned governments and peoples to hound the terrorists out of business.