I guess in the coaching of high school students that I do, I think that students in high school are a lot less independent in general that my peers were 10 years ago. Cell phones are only a part of it, but if the way tv commercials market cell phones is indicative, then it's a fairly important part.
What better time to lose the electronic leash than college? It will be hard for your parents that you won't be at their call whenever they want you, but they'll learn to deal with it. After all, they have brought you up well with good, sound judgement, so this is when they can let go a little more. Especially because at Whitman most of your experience is on campus and cell phone coverage sucks when you're hiking in the Blues and you don't want to drop the phone in the water when you're kayaking.
Then again, I only called my parents one a month or so when I was in college. I'm the youngest of 4 kids, so they had learned to deal with separation issues.
The good news if you decide not to have a cell phone is there are telephones in every residence hall room that will connect to your parent's home if there is an emergency.
ps- any incoming students should spend the summer learning how to do their own laundry if they haven't had the pleasure yet. There were a handful of students in my freshmen year hall who honestly hadn't ever done laundry in their life.