Opinion divided on legacy of sport events

An intense debate is currently raging in the UK about the legacy sporting events such as the Olympic Games can have, with some people believing the impact can be massive (e.g. evidence indicates the 1992 Barcelona Olympics generated upwards of Euros13 billion worth of economic benefit), while others think any benefits are entirely negligible. But what is 'legacy'? Is 'legacy' purely economic? Or can it be socio-cultural, psychological, physiological and more besides? How should one (does one need to?) measure legacy? And how should sport events be organised and managed to ensure the 'legacy' effect is optimised?