The resource I have referenced for you has a mention of a 70-person brawl that took place at a shopping center, largely participated in by teenagers loitering about that area of the mall. The useful reasons should be fairly obvious, in that the device is designed towards a younger age range. That age range characteristically will seek out areas to populate for socialization. Sometimes, the activities involved in these social settings are not conducive to the normal business atmosphere that attracts the money-spending public, so customer traffic is reduced. I myself have been witness to a major mall in the southern part of our metro area going out of business, largely due to loitering of unsupervised youg people. Customers simply won't go where the threat of crime is higher, they will find other safer venues to participate in. The antiloitering device doesn't seem to have any negatives at this point, except maybe for those young people who actually do fall into the customer side of the equation. People older than 25 don't find the noise the device makes to be distracting or annoying.