Probably the smartest thing that LOCOG have done in seeking to engage the UK population is to go local.
By that I mean going 8000 miles over 70 days and visiting countless "locales" - i.e. places where real people live and thrive with other people. The hard yards, you might call it.
And to create the sense of shared excitement for those on the route - offering the chance to thousands of people to participate (and compete to do so) each of which is recognisable in their own locale - it seems to have followed all the rules of the modern engagement strategy.
But it is a fantastic social diffusion idea: gathering crowds of people familiar to each other - or from the same place, at least - getting them excited with anticipation and getting them to see and feel each others' excitement. Flags, cheering, crowds, epic journey - all of these help.
Simple stuff, you might think but not something marketers today can be bothered with doing.
Go where the people are (rather than just shout at them).
Give them something (interesting & fun) to do together.
Help them see the excitement of those around them and those before and after them.
And start well ahead of time (building your audience's excitement well before you need it).
Not tricky, is it?
Key learning is this: audiences are not individuals acting independently - pairs of eyeballs or whatever the media measurement guys count.
Audiences are individuals interacting with each other around your activities. The more you encourage this further things spread.