I agree with the non-rev who called you out if it was a phone. I see these morons all the time acting like 2 year olds hiding their backberry's when the FA comes around to pull it out and tap tap tap away as we are taking off. I don't know what the possible issues are but the rules are there for a reason. I don't want my life risked because some idiot isn't efficient enough to get their work done during their normal business hours.

From FAA website:

Federal Communications Commission (FCC) rules prohibit the use of cellular phones using the 800 MHz frequency and other wireless devices on airborne aircraft. This ban was put in place because of potential interference to wireless networks on the ground.

In March 2007, the FCC terminated a proceeding that it began in late 2004 to consider potentially lifting this ban. The FCC determined that the technical information provided by interested parties in response to the proposal was insufficient to determine whether in-flight use of wireless devices on aircraft could cause harmful interference to wireless networks on the ground. Therefore, it decided at this time to make no changes in the rules prohibiting in-flight use of such devices.

In addition to the FCC’s rules, the Federal Aviation Administration (FAA) prohibits in-flight use of wireless devices because of potential interference to the aircraft’s navigation and communication systems. For this same reason the FAA also regulates the use of all portable electronic devices (PEDs), such as iPods and portable DVD players, during flight.