The Hardball Times says so.
Not going to go into an in-depth analysis, but suffice to say, a book, aptly titled The Book, argues for the legitimacy of "the second leadoff hitter theory."
Quoth the HBT:
You gain more by having a good hitter bat directly before your top hitters than you lose by giving your pitcher a few more plate appearances each year. I'm not talking about Jason Marquis or Dontrelle Willis. I'm talking about your bad-hitting pitchers. Move them up a spot. In fact, this strategic guideline argues AGAINST moving Marquis and Willis up in the order.
A couple of extra runs doesn't sound like a lot, but if you follow theses guidelines, you could gain 10-15 runs over a full season. About a win a year.