"at this time, please discontinue use of portable electronic devices"

I'm disappointed. As much as I want to roll my eyes when the flight attendant requires me to shut off my Treo, it turns out that reputable sources are actually viewing cell phones on planes as dangerous. This article, from earlier this year, was published by the IEEE Spectrum (read: "eye-triple-eee"), the same respected electronics journal that arrives at my house monthly for my roommate working as an electrical engineer.

While they remain reserved on saying your iPod or DVD player could actually cause a crash, they used hidden on-board testing equipment to discover that 1 to 4 people a flight are ignoring the rules and making live cell phone calls while airborne - and it's the phones they say can cause real trouble:

In March 2004, acting on a number of reports from general aviation pilots that Samsung SPH-N300 cellphones had caused their GPS receivers to lose satellite lock, NASA issued a technical memorandum that described emissions from this popular phone. It reported that there were emissions in the GPS band capable of causing interference. Disturbingly, though, they were low enough to comply with FCC emissions standards.

Our data and the NASA studies suggest to us that there is a clear and present danger: cellphones can render GPS instrument useless for landings.

read the whole article: "Unsafe At Any Airspeed?" By Bill Strauss, M. Granger Morgan, Jay Apt, and Daniel D. Stancil