Not that I like the idea of shutting any of them down,
but the reality is, post to a web page and you notify dozens, hundreds, thousands, or millions. Make a phone call from a mobile and you communicate with one. Yes you can setup phone trees, but that takes pre-planning, shows malice, and requires a leader against whom leverage can be applied. So there is some logic in what he is proposing.
A better idea would be to use social media to mobilize the population for self-defense and real community self-policing. The problem there is, you Brits are about 20 years ahead of us 'Merkins on the march of Progressive Fascism to the soft totalitarian communist state, so that concept is anathema to anyone in government. Although I will give the citizenry fair marks for the other night: actually engaging in just that sort of self-policing seems to have broken the cycle. A bit late so I can't grant good marks, but better late than never and if you build on it, you just might start taking the first steps away from economic stagnation, possibly even leading Europe to recovery.