Who could have anticipated the attack?

[jaguar]

It was extremely cheap to load a raft with explosives and send it out to try to sink the USS Cole. The Coast Guard is hurting for funds and can't possibly guard the coast. There are a ton of interesting targets along the coast. A hole in an oil tanker at a port city would be enough to cause a big ecological problem, and might even have a geopolitical impact as well.

I still think ships are the biggest risk, either blowing on up, particualry LPG or Oil tankers while in port or loading one with someing very nasty. SO much space, fly it under a flag of convenience and the acutal owner etc is virtually un identifiable.