OK, I'm the guilty one. (I wish there was some way to separate the cabin walk through and the non-emitting PED's. In fact, IPODs don't harm anything and as long as someone does not mind looking a fool, then they should get to enjoy their music.)
When we know it is going to be bumpy down low I turn on the seat belt sign and notify the FA early so they can get their walk through done and prepare the cabin before we encounter turbulence that might result in an injury. Usually this happen just below 18,000, but if the build ups are in the mid twenties and ATC can't let us deviate as much as we like, then the bells happen earlier.
Then final approach control gets a hold of us and vectors us out for a 25 mile down wind (ATL) and it does seem like it takes F O R E V E R to finally get down and in the gate.
Sometimes I think, "darn, got the sign too early." But that sure beats even getting a minor injury which is supposed to be reportable under most Companys' FOMs. There was a FSDO that handing out 60 day suspensions for crew/passenger injuries that they heard about - even with the seat belt sign on. Around ATL it has not happened that I am aware of, but different FSDO's have wildly different enforcement philosophies.
If you are travelling in uniform, try this approach - be nice. Raise our profession by being the kind of professional who can answer a question with a smile. Don't we all like it when kids point at us in uniform and say "look, a pilot, that is what I want to be."
Used to be that pilots were all over third grade bulletin boards. Now the Firemen have a commanding lead. Lets take it back.
On the flip side, on a 05:30 flight (yawn) in smooth air - expect the bells and seat belt sign just before 10,000.
Sure the book says "10,000," but the goal is to keep the crew and our passengers safe.