Note page 2 of the subpoena: "18.104.22.168 at 6/27/2003 at 9:29 am (EDT)". Forty-one characters. That's all it takes.
The subpoena was refiled on August 25. There has not yet been a response from MIT, as far as I can tell. According to an article in The Tech (MIT's student newspaper), the username was 'crazyface' at KaZaA, and the federal Family Education Rights and Privacy Act requires that MIT take "a few days" to "notify a student that their records will be disclosed and give the student a chance to contest the release of information". It has now been 11 days since the filing date.