Al-Qaida has been "the usual suspects" for so long I find it hard to believe they're responsible for everything that gets attributed to them. Why would they strike Spain. Spain doesn't support Israel (very much, if any), Spain doesn't oppress their people, etc. Logical targets would be Britain or America if they wanted to strike back at the people who (you think) hurt you. I'm not saying its not possible they're behind it, but I think that blaming Al-Qaida for every act of crime is more than likely just a way to rally people against a specific target, and due to their ethereal nature (when it comes to slipping in and out of a country) it's very easy to convince people that certain reasonable security measures are neccessary to defend against them.

Adrian