I understand that the Spanish ID system for 'foreigners' is called a " Residencia " which is on a par with the Carte de Sejour that used to exist here in France; it is a permit to live and work in that country. We held a Carte de Sejour for 10 years up to 2003 when they were deemed no longer necessary for EU Member State nationals. (I am aware that the Residencia in Spain is still in operation, but I think it is a choice for individual Member States) On our CdS there was a photo, name, address, d.o.b. and nationality - they were very useful in instances where ID had to be deposited, which is the case in some Hotels and camp sites throughout Europe and we also used them on flights to other European countries (except the UK !) in place of our Passports. However, identity papers are definitely required here for NON EU Member State Nationals. The French Nationals do have ID cards, which they are able to use as a "Passport" for flights to other EU Countires (except the UK) The ID cards contain the same information as our CdS did.
Reading about the information the UK Government intend to apply to their ID Card system, is mind boggling, and I remain cynical in that this particular Government is hell bent on building a data base on every UK citizen, the consequences of which could be startling to say the least. They use the 'terrorist threat' in such a way that it could be construed as emotional blackmail,and I totally agree with Exo that anyone who is intent on causing mayhem and destruction will not be deterred by an ID card. The present UK Government are intent on surveillance to the point that if it wasn't so serious it would be farcical.