We all know that Barack Obama (or at least, his staff), is on Twitter, sending out messages under @barackobama. Turns out, so are lots of world leaders (or rather, their surrogates). There’s Toomas Hendrik Ilves, the president of Estonia. There’s Dmitry Medvedev, the prime minister of Russia. So are the leaders of Canada, Mexico, Brazil and Rwanda. Heck, even Ayatollah Ali Khamenei, the Supreme Leader of Iran, is on Twitter: @khamenei_ir.

What does this all mean? No one is quite sure yet, although there are some folks like Matthias Leufkens, formerly of the World Economic Forum, that have been examining "Twitplomacy" for a few years now.

But this week, some journalists over at the Agence France Presse have put together a neat interactive online tool, called E-Diplomacy, that shows which countries follow which others, how much social discussion is going on between various countries, diplomats, and world thinkers.

There’s been a lot of discussion in the media and popular opinion around the "Twitter Revolution" that wasn’t in Iran in June 2009, which was later bolstered by last year’s Arab Spring that saw a significant change in government in many North African and Middle Eastern countries.

"We do know this: Twitter and Facebook, when used by activists, can be very efficient tools to mobilize, to communicate with one’s peers, and to broadcast to the world what's going on in an area where it's hard for reporters to work," wrote Joan Tilouine, the editorial director of the project, in an e-mail sent to Ars on Friday.

"At least at the margin, these forces can bolster an "offline" movement by women and men in the streets. But whether the outcome is further repression, the implosion of an autocratic regime or even a revolution depends on many, many factors. There is a further question, one that the post-revolt states in North Africa or now facing: can social media help build democracy after the fact? Can ‘followers’ and ‘friends’ generate new leaders? The answer to that one is still in the making."