Tweeter is both powerful and risky as a tool for politicians. This is the main message in the Economist article on Twitter. Although it focuses on politicians, many aspects could apply to diplomats as well. As an illustration of the power of Twitter, the Economist starts with, what else, Obama's campaign, but it also mentions other prominent tweeters including Pinera (new Chilean president), Chavez and George Papandreou. The article concludes that twiteer is good for campaigning and opposition, which are usually in "digital" (black and white), but not an ideal tool for a messy policy discussion (very analogue - contradictions, paradoxes, etc.).
The risks of tweeting are numerous. Politicians, like diplomats, might tweet something that will haunt them. But the problem is that risk-averse tweeting (like all of social media) is not particularly attractive. Nobody reads bland tweets. People look for some spice. As any good chef knows making spicy and tasty food requires special talents. It also applies Politikh Kouzina!