Guest post by Matthias Lüfkens, Associate Director of Media, World Economic Forum – Follow him on Twitter Twitter is redefining the way we communicate – and that includes our world leaders: 15 of the G20 governments use it. But the question is who follows who, who doesn’t follow who, and do world leaders even realize the diplomatic significance of their tweets and Twitter friendships? Barack Obama was the first to use the micro-blogging service to communicate with his electorate in…