The question assumes that there is an identifiable difference moving forward. Is a digital outdoor screen classed as a traditional billboard or a digital ad? Is a targeted commercial fed to your set top box a traditional television ad or a digital ad? Is an advertisement inserted into the audio stream of your favourite radio station a radio ad or a digital ad? They may be bought and sold in ways that are similar to their "traditional" counterparts but delivered to smaller, segmented audiences by technologies we class as digital. I agree with Chris, the distinction is not really relevant. If a there's a large image across the railway tracks at the metro station does it matter if somebody's had to get out there and stick up sheets of paper, if it's projected and changed every few minutes or if it's activated in some way by your presence & delivers something relevant to you? It's still a large image across the tracks. I wonder if the distinction is helpful or a hindrance?