This 2008 article from the Boston Globe is a good reminder of the risk students take when they receive too much help with their applications.
Whether you’re a parent, a counselor, or any well-meaning advisor helping a student apply to college, remember that over-editing, over-polishing, or otherwise becoming too involved in the process usually leads to applications and essays that smack of too much help. And few things will cast doubt in an admissions officer’s mind faster than materials that are just too good to be true. Advise, guide, and edit, but make sure the application remains literally and figuratively the student’s.
My favorite quote from the article:
"There's a little bit of a disconnect sometimes," said Gil J. Villanueva, dean of admissions at Brandeis University. "We expect people to write like 17- and 18-year-olds, and sometimes it comes across like it could be in a book."