The finest Olympics revitalize rundown districts, inspire young people into sport and leave a city with fantastic sites and a healthy profit; Barcelona is a good example of this. The worst leave nations crippled by debt and half-dead venues - look no further than Athens.
The Olympic legacy London hoped for when it won the bid in 2005 was to inspire a new generation of sportsmen and women and to regenerate a rundown area of East London, without the facilities being a drain on public finances. Prime Minister David Cameron told a recent press conference he expected the Games to generate at least $1 billion for British businesses.
So far six out of the eight Olympic venues have secured their future, but the prospects for the centerpiece of the 2012 games - the Olympic Stadium, which cost an estimated $760 million to build - remain uncertain. This is also true for the Olympics Press and Broadcast Centre.
Whether the games will boost young people's participation in sport is less clear. The Chairman of the British Olympics Association, Colin Moynihan, recently told the Observer newspaper that since the UK won the 2012 bid politicians have failed to honor pledges to drive through a national sporting revolution and unless there was a last minute change in policy, the games would spur little improvement . As for the cost, it is looking increasingly likely that London will breach its $14.3 (Euro 9.3) billion budget because of rising transport and security costs.
It is too late now for London to learn from the experiences of previous host cities, but the lessons are clear to see. Click ahead to see some examples of winter and summer Olympic booms and busts.
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