The reason that Ryanair requires photo ID in the form of a passport or photo driving licence is that they have been hit very hard by online ticket fraud
Well, fair enough! If thats the real reason, why lie and blame it on security? There's obviously a financial reason for rules like this, whether it be credit card fraud or just the passing on of unwanted tickets. What they are in effect doing (and I mean all the lo-co's, not just Ryan) is basically making an extra few quid from September 11th which is disgraceful.
I'm sure BA etc. have the same fraud problems. For domestic flights, I buy an E-ticket online with credit card, check in at a machine and never see the checkin staff. Why are BA less likely to have the same problems as Ryanair? Answer - they aren't, it's just that they don't stoop so low to make a few quid in the name of security!
Oh, and just in case - I totally agree that however stupid the rule, it should be applied equally to everyone - well done Ryanair for that, at least.