A few months ago there was that one annoying digital billboard on our drive home, flashing unwelcome news about the new Alvin and the Chipmunks movie. Now digital billboards are popping up all over L.A.Clear Channel Outdoor's chief executive Paul Meyer explains the benefits from the advertiser's perspective: "We're there 24-7...There's no mute button, no on-off switch, no changing the station." If only Clear Channel could keep people from blinking.In a city like L.A., with an already crowded visual environment, more digital billboards isn't a huge disaster. In a smaller town or a suburb, though, they could be a real blight. And advertising companies all over the country are pushing cities to allow them to convert their billboards to digital. Should this be stopped?From Rob Walker's del.icio.us links.