Usually depends on how well it's wedged into the pocket. I usually see them speak up when people have made a halfhearted attempt, like shoving it into the tiny too-small water bottle pocket tip first with the main body of the bottle dangling out, or nestling it in a pile of magazines in a bulkhead pocket, or clipping it into the pocket with half the bottle still visible where a bump could cause it to launch out the top of the pocket. I've never seen anyone object if the bottle is shoved all the way down into the pocket and no longer visible.
My solution is simple - wedge it between my posterior and the corner of the seat. Never once had an objection with that strategy
