Everybody I ride with has a bell on their bike. One of the two fellows who gave me my bell has two bells on his '08 FLHTCU.
His 16-year-old son just bought his first Sporty last week and I bought him a bell for his bike.
I bought a bell for my wife for her new bike this weekend. She forgot to retrieve her bell off the old bike when she traded up from her '07 FLSTC to a new '09 FLHX. She got her first bell when I got mine -- from the same two friends. Her '05 XL1200C had a mildly eventful journey to Myrtle Beach and they felt it was probably a good idea to get her "belled up" before the ride home. It mostly worked. The ride home was uneventful except for losing the clevis pin on the front brake lever about 100 miles out.
The bell on my SERG has been on all three of my FLTRs. It was given to me by two best friends on our first trip to Myrtle Beach. I know this one worked. I've had two mishaps during this bell's tenure.
One incident was a run-in with a Hummer. The bike took $14K is *cosmetic* damage, but we were able to finish our trip.
The other incident was a pully that sheared off at the axle at 85mph. Not too much traffic around, so we coasted to the shoulder and called a friend who brought my trailer and towed us home.