I am a commuter between Brisbane and Melbourne. In the last 6 months I have noticed a trend for passengers to simply ignore the requests of crew to "switch devices to flight mode" so much so that on four occasions in the last couple of months passengers have initiated or received phone calls on taxi out or, on two occasions, on the take off roll. In each case the crew ignored it despite it being quite obvious who was infringing the policy.
I'm sure it's the same on all carriers, but I find it frustrating that an announcement is made, the majority of passengers ignore it and no-one thinks that it may be necessary to either allow the use of these devices or actually make some effort to ensure compliance with a regulatory requirement.