The scale of the terrorist siege at Nairobi's Westgate Mall, which now appears to have finally ended after four days, may have been unprecedented. But the notion of shopping centers as tempting targets for terrorist attacks is hardly new.
A 2006 analysis from the Rand Corporation warned that, "in terms of their potential role as terrorist targets, shopping centers present numerous challenges for security." At the time, they reported that there had been over 60 terrorist attacks against shopping centers in 21 countries since 1998. There have been several reported international terrorist threats against malls in the United States over the years, though none have been carried out.
Obviously, any "soft target" where large crowds of people gather are going to be tempting for attackers. Malls "allow unimpeded access to the public and attract a wide cross-section of the nation's population," the Rand authors write. But they also suggest that the business model of malls makes the marginal cost of additional security measures extremely high and leads to most of them being relatively unprotected.
Shopping centers "differ markedly from facilities like airports, which provide an essential service with few alternatives," they write. "For this reason, shopping center customers and tenants may not tolerate the expense and inconvenience of increased security." There's also the fact that malls often have complex, multi-stakeholder ownership structures which "increases the difficulties of implementing security and other risk-reduction measures."
The authors say after a catastrophic attack, customers and businesses might become more tolerant of security measures like metal detectors, as they did with airports in the wake of 9/11. However, events have shown that even measures that the public wouldn't tolerate in most countries might not be enough to keep customers safe.
In the wake of a 2005 bombing outside the entrance to a shopping mall in Netanya, Israel in 2006, The New York Times noted that "Most shopping malls, stores, restaurants and other public buildings in Israel have guards and often metal detectors at the entrances," but unfortunately, "the checks also create lines, which sometimes become targets."
Again, the Nairobi attack was a unique case. The Westgate mall is a potent symbol of Kenya's rising middle class - in stark contrast to neighboring Somalia - and also attracts an international clientele. But it's definitely the first time such a place has been targeted, and assuming most countries aren't willing to turn malls into fortresses, it's probably not a threat that's going away.