Hum... you should think it is. Cellphones are simply more conveniant, and cheap. Seriously, from my point of view, punks, hippies, technocrats, fratboys, etc.. all of them have, in pretty much equal number, cellphones. Older peoples, however, have different habits.
We can opine about that, but for pollsters to have credibility, they should know what it is. I think they have some homework to do as the trend is increasing, not going away.
Oh, and there is another group (as I just found out - I just got caller ID).
Those with Landlines and caller ID. LIke I am going to answer an 800 number! 