And then a street vendor in Tunisia sets himself on fire. It strikes a chord in the people, they gather in forbidden numbers. The penny ante dictators in one fragile society lose their nerve and flee. An example has been set, a new possibility emerges into the public consciousness. Nothing has really changed except where before there was only a blank wall of fatalism and resignation, now there is a road, a possible path to a better future. People see that road and they take it.
That is the revolution equation. When the sum of the people's political expectations exceeds their economic expectations, they are ripe for revolt. It takes only a spark, a Facebook post or a timely tweet. It only takes an idea.