Security in Public Places

How secure are public places really? Since the Virginia Tech shootings many college campuses have felt the need to bump up the security. However, does this increase in security give students a false sense of protection. For example say you have to have an ID card to open buildings on campus. The fact that it is locked may make students feel at ease and assume that nothing is likely to go wrong. Yet some students hold the doors open, thus, inviting unexpected visitors in. Another example is in my neighborhood we have security guards that patrol the neighborhood 24/7. Naturally, I assume that a burglary is unlikely to happen because the security guards would see something. Unfortunately one night 7 houses on my street were robbed. Though an increase in security may reduce random assaults, I believe its unlikely to prevent pre meditated ones. If someone really wants to do something they will wait and find a weakness. On the other hand if you increase security even more it can became a bother or result in the loss of your privacy. How willing are we to heighten the security around us? I often hear people complaining at air ports about how strict they are; you cant even carry a liquid on the plane over a certain oz amount, and even legal the items must be in a plastic bag, or you have to throw them out. How much of our privacy are we wiling to give up for a little extra protection, and does this extra security actually prevent anything or is it just to make us feel better?