I might have mentioned this before on here, but this stupid government directive has finally kicked in yesterday! It's supposedly aimed at trying to cut down on bombs being triggered by unregistered prepaid mobiles. Of course, there is nothing stopping them using an unregistered foreign SIM that is roaming here though!
If members here happen to have a Spanish Prepaid card that has been cut-off, you have 6 months grace in order to register your SIM in your name!
If you can read Spanish there are more details on:
Los clientes de móvil prepago tendrán seis meses más para identificarse · ELPAÍS.com
Also an Article in English at:
Spain cuts off 3m pre-pay mobiles ? The Register