I used to work in an office that had a cell phone policy. You were not allowed to talk on your cell phone, and/or allow an audible ring.
Back then I hated the policy, I thought it was ridiculous, and that people would self-regulate their activity.
Now I work somewhere where I hear a ringtone every hour (just for fun, yesterday we averaged one ring every 25 minutes), and it's not a regular ring. I hear the Wizard of Oz, Chipmunks, and a host of other tones, far more distracting than a normal phone.
So I guess it's safe to say the pendulum has shifted slightly. I still hate the no cell phone policy, but now I dislike custom ring tones (at least in the office).
So what's the solution? Make your office policy to set all cell phones to vibrate rather than ring? Sounds good to me.