Some people are so beguiled by a new piece of social media technology that they overlook the message they are using it to deliver. Of course, finding more efficient ways to deliver our points is always a sensible quest, but we must never forget that social media, and social networks, are tools, not an end in themselves.
Permit me to take this a stage further. If you have a powerful, timely message, it will be heard regardless of the methods you employ initially. You may decide to run a YouTube campaign to promote your latest book. People may start talking about it on Facebook, which attracts the attention of broadcast media, such as TV and radio. Before you know it, you have a wider audience using channels you hadn't planned to use that in the media that you had carefully planned for.
That's why, in my opinion, all campaigns should start with the core message, and then seek the best way of delivering it. You should also be prepared to switch your media focus at short notice. It's not about the medium, it's about the message. Maybe that's not the way Marshall McLuhan would have seen it, but it's my take.