What helped the the Egyptian revolution the most: Twitter, or the government switching it off?

I have been really interested in the “meme” that the Egyptian revolution was “the first social media revolution” and have tolerated infographics that correlate specific twitter activity with events in Egypt beyond. And I am sure we have all reminded ourselves that correlation is not causation.
I was recently listening to an Egyptian colleague who was in a position to know something about this. What he said was interesting: the revolution only really took off during the six days when the government switched off mobile phone networks and the internet. Up to then, these technologies had been quite useful in organising specific protests and plumbing the depths of support. But when that all went dead, there was nothing left to do but actually get out on the streets. And that’s when it all really took off. Plus, as he put it, there were a lot of young lads who suddenly realised that their Dads couldn’t reach them on their mobiles any more …