You could make a case for the notion that a mobile gadget hasn't really arrived until the nation's airlines feel the need to mention it explicitly when telling you what you can and can't do in flight.
I was struck by that thought when I flew to Boston and back and found that the flight attendants on both planes specifically discussed noise-canceling headphones (such as Bose's QuietComfort models), pointing out that they run on batteries and therefore should not be used during those periods when use of electronic equipment is required. It was the first time I'd heard these headphones singled out, and I imagine it's a sign that there are of a lot of them in use in the air these days.
(Side note: Sound-isolating headphones such as the Shures I use don't have this limitation -yet another reason to love 'em, along with the fact that they take up a lot less space than noise-canceling models.)
Airplane announcements may get updated regularly: those seat-pocket information cards, however, are kind of timeless. A cell phone on an information card looks like it dates from about 1997; the radio could be one I bought in the 1980s. The basic message here is "Don't use stuff with antennas!” but in an age when a lot of the gadgets we take aboard planes (such as laptops) include embedded antennas you can't see, and in which it can be okay to use devices with antennas (such as my BlackBerry) if you disable their wireless functionality, it's tough to be both comprehensive and precise with a series of pictograms.