Perhaps surprisingly, the answer is Ben S Bernanke, under the guise of the Federal Reserve. Tweeting as @federalreserve, the idea is that it will be more transparent to the public and to anyone who is curious to know what is going on in the financial world.
It is early days when it comes to its follower count, but the fed managed to add 1,500 followers in the first hour of the Twitter feed going live. At the time of writing, it was nearly up to 14,000 followers, so things appear to be going well at the moment. However, there have only been six tweets so far. These have included messages about when Mr Bernanke will be speaking about the financial crisis and a link to a report about financial services available via mobiles. Useful links are included in these posts so it could be a good resource for those who are interested.
It is another example of how major companies are getting in on some Twitter action. If you are famous or at the head of a big company or organisation like this, you can be sure you will get thousands of Twitter followers in a very short space of time indeed. Going on Twitter does make the Federal Reserve more accessible for people who are firmly entrenched in the social media age. It also provides people with ways to find out more about the Federal Reserve System, so it could be quite educational if you persist in following it.