Both Duke Fuqua and Michigan Ross have recently admitted they've adopted plagiarism-detecting software that will help them spot applicants who are copying essays. Duke is using TurnItIn according to an excellent article in the GettingIn blog at BusinessWeek. while Ross wasn't so specific about the software they were using in a recent posting to their Ross Admissions Blog.
This is a growing trend, and if it is helping schools identify applicants who are purchasing admissions essays or handing over the writing duty to a third party, then I think it's a good thing. There's nothing wrong with getting a second opinion on your essays - I encourage it! On the other hand, using ghostwriters, heavy-handed editors, or the essays used by someone to get admitted before you is not just dishonest - it is just plain dumb.