Bruce Schneier makes a good point in this article on Movie Plot Threats:
I wonder why he thinks that “schools, churches and government or medical facilities” are terrorist targets worth protecting, and movie theaters, stadiums, concert halls, restaurants, train stations, shopping malls, Toys-R-Us stores on the day after Thanksgiving, train stations, and theme parks are not. After all, “there’s got to be some common sense.”
Yes, and the same technology that allows people to call their friends can be used by terrorists to choose targets and plan attacks. And the same technology that allows people to commute to work can be used by terrorists to plan and execute attacks. And the same technology that allows you to read this blog post…repeat until tired.