On July 7, 2005, one day after Londoners received word that the city would host the 2012 Olympics, terrorist bombs tore through the public transit system, killing 56 people. To prevent a repeat attack and protect the roughly 25,000 athletes, family members, coaches, and officials attending (along with roughly 700,000 spectators), spending on security has topped $1.6 billion. Sydney's pre-9/11 Olympic security in 2000 cost only $179.6 million.
Some privacy advocates have questioned the efficacy of such huge outlays of taxpayer cash. James Baker, the campaign manager for the privacy organization No2ID, points out that in May, a concerned workman at The Sun tabloid was able to smuggle a fake bomb into the Olympic Park in spite of spite of iris and hand scanners at the site. Baker also wonders if authorities will be able to use the web of surveillance technologies quickly enough to be effective -- he points out that in 2009, several of the more than 10,000 license plate scanners around the country detected the car of Peter Chapman 16 different times -- he was wanted for arson, theft, and violation of his status as a sex offender. But police were inundated with hits from the system and did not follow up. Two days later, he raped and murdered a teen he met via Facebook.
More from our own Andrew Rosenblum in CNN Money magazine.