I find it terrifying that the most cloistered society in the history of the world can't raise children with enough sense and self-discipline to use a cell-phone responsibly. If the yeshivas are worried that their boys are using cell phones to download porn - or even if they worry that learning sessions will be irreversibly shattered if news from the outside world filters in- something is seriously amiss in those four amot.
Still, they can do, as they like. If cell phones can be banned in gym lockers, they can be banned in the yeshivot.
DOWNSIDE: There will be no more snapping and sending erotic bes medrash pics via photo-phone for me, I guess.