Yes, it's really him. There's the "Verified Account" logo, the nearly 200,000 followers in less than a day, the link to his foundation's Website, and the "Sharing cool things I'm learning through my foundation work and other interests" bio squib.

I can only assume that other people have tried to create fake "Bill Gates" Twitter accounts in the past, if only so they could fool the gullible into believing that the world's richest man would actually tweet missives such as: "DUUUUDE! BEEEER PONG!"

Gates' first post was "Hello World." I assume that's a nod to the "Hello World" program traditionally written by people learning a particular computer language for the first time.

Gates is currently following 40 other Twitter feeds; his biggest Twitter partner of the moment seems to be ubiquitous radio/TV host Ryan Seacrest, with the two of them exchanging tweets about aid to earthquake-ravaged Haiti. He also sent a message to Ashton Kutcher, thanking him "and all the other people who have welcomed me."

Gates has also rejoined Facebook, having taken down his page in July 2009 after being inundated with friend requests. At the time, Gates apparently had trouble figuring out whether he "knew this person, did I not know this person," according to news sources. (If you're worth $40 billion, though, couldn't you hire a team of people to vet Facebook friends for you?)