Ever heard of the Stasi? Read up about them, and you'll understand. As for terrorists being private persons, well guess what. No terrorist has been caught by illegally invading his private space. Ever. They are caught by investigation, intelligence informants and the use of warrants.
What happened last time they didn't get a proper warrant? That idiot geelani got off from the parliament attack case. And the attack did take place. Use a warrant and I have no problems.
As for searching when there is a suspicion, well, let us hope they do so properly. The question is, what do they suspect you of, and what do they search for? As I told you, the chance of finding a criminal like that is low, but you are sure as hell harassing innocents.
As for idealism vs realism, guess what. The lack of privacy is the biggest security risk. If you go and collect information on people (and that is what a lot of these hairbrained schemes mean), it will easily be sold and misused. Look at it this way - terrorists often get fake passports. But if you investigate them, you can find them out because they have built up fake records, and at some point you'll find a break, and be able to catch them. But if you build up complete records of innocent people, well someone or the other will bribe or break his way in, steal the entire (real) background of someone and then you have identity theft..... when the thief is a terrorist, that is all the more dangerous.
There is little chance of someone going to jail over sms, and even if he did there would be a complaint against him.
Wow, you certainly trust the cops. Ask superczar about how they got a few thousand rupees from him on a routine traffic stop when they didn't even accuse him of a criminal act, just something he never did understand. The point is this - if a guy breaks a signal, bust his ass by all means. If he does something more, go ahead and arrest him. But stopping people and looking at cell phones is a bad idea. You really are getting into things you shouldn't. And you are also pushing away a lot of avenues you do have. Guess what, some terrorists probably do use SMS for sending terror related communication. Right now, we have a chance, if we know who they are, to monitor that communication and find out what they are up to. If they think that they are going to be stopped at traffic lights and frisked, they just won't use SMS for such communications. End result is that even a wiretap won't work! I am terrified that when the US decides to wiretap everyone's lines and all the internet, all that will happen is the terrorists will start encrypting their email. As of now, encrypting email is painful and not easy in most throw away webmail accounts (the kind these guys use). But once wiretapping is common, trust me, everyone will start using this... and so encrypted emails won't even stand out.
How many are you likely to find? I don't know, but i sure would want to find them out rather than they finding someone out
Ah, but they have never found anyone out like that! You just don't get those breaks in real life unfortunately. Let me also give you a hint on security - random checks are often better than mandatory checks. Mandatory checks are possible only at a very few control points and are more of a lets stop amateurs from doing something stupid, or if you have specific information, as opposed to criminal doing something criminal, and random checks are only useful at certain high risk areas.
You know, suppose you do get a sharp object on to the plane. They aren't really worried about that (if they find one in your bags, all they do is throw it out and let you go; clearly they don't think you are a terrorist). What they are worried about is if a terrorist, who did not have a weapon, takes that from you and uses it as a weapon.....
My point here is that a lot of what people are talking about is just security theatre - an attempt to pretend you are doing something when you are not. Unfortunately, it does not really scare terrorists - those guys are willing to kill themselves, so you can't use the fear of capture against them.