I think Lance won the TDF Prologue last year while averaging just a smidgen under 30 MPH.

I looked that up a while back to bring a dose of reality to some guy claiming he was doing nearly 35 MPH on an out and back 10 mile ITT. He said he was sure he would have topped 35 MPH if he hadn't been slowed by traffic. uhm, yeah

edit to add: 2002 TDF PRologue results - 7 kilometers (4.34 miles) in 9:08:78 or 28.46 MPH after which LA said "After seeing the split times all day, we knew the race was going to be won or lost in the in the last kilometre," said Armstrong in the post-race press conference. "It was really hard. Personally I was cross-eyed."