It appears to be a hoax, not real terrorism, but does raise an ugly spectre.
All around the world, terrorists wage unconvential war against 'the west' (mainly).
The few 'western' terror cells (Basque seperatists, IRA etc) usually provide warnings.
If some citizens in the western world decide to adopt muslim extremist tatics - one shudders to think of the consequences.
A government with superior military techonology + active domestic terror networks against another culture = game over.
The clash of the civilizations just got a whole lot scarier! let's hope they catch the loony and jail them for a little more than the bali bombers got!