“Last October, we launched Instagram live in the App Store. Today, less than one year later, we’re happy to announce that the Instagram community now consists of over 10 million registered users.”
Account number 10 million is “homer123” (view on Statigram) but it has not posted any photos yet. Since account number 1 and 2 are missing (first working account is Kevin Systrom at #3), you might say that the 10 millionth account is 10,000,002: “dinbeebis” (possibly Swedish?).
Instagram is also close to reaching a quarter of a billion hosted photos since photo number 240 million was uploaded this morning: http://statigr.am/viewer.php#/detail/240000000
Hat tip to Feber.se. I am “kullin” on Instagram.