I can see two possibilities as to the motivation for this atrocity. The first is that it was an attack on Western civilians by Al-Qaeda associated individuals, simply because they were Western. Kuta in Bali is an extremely soft target in this case: nowhere else in Indonesia would you find so many westerners in so small an area. (Also, the Balinese are Hindu, so you avoid killing Muslims at the same time). Still, given the virulent anti-Americanism of these organisations, the choice of a target where Americans are almost completely absent is perhaps a little curious. (The apparent smaller third bomb outside the US consulate might favour this theory, however, as would the fact that the American ambassador has been warning about possible attacks).

The other possibility is that it was an Indonesian nationalist attack rather than a Islamic attack. Australia has (in the last couple of years, at least) supported independence in East Timor, has supplied the bulk of the peace keeping force, plus there have apparently been Australian SAS troops in the mountains keeping an eye on things. This could be an attack aimed directly at Australians out of revenge for the loss of this territory. Early October is a peak time for Australians to visit Bali, as it is just after the end of the football season in Australia. Bali was a favourite destination for footballers wanting an end of season trip to let their hair down. I don't know if the terrorists realised this and took it into account, but they may have.

Of course, it isn't necessary as clear cut as this. There have been rumours of Al Qaeda trained individuals being involved in East Timor, and of course Australia is a good friend of America, so maybe its a mixture. Either way, it is vile beyond belief. Australians are not used to this. (Not that I imagine that it gets any easier to deal with if you are used to it).