Oracle Text

X, T: Choose a card name. Target opponent reveals X cards at random from their hand. Then that player discards all cards with that name revealed this way. Activate this ability only during your turn.

Card Rulings

10/1/2009 You don’t name a card until the ability resolves. Once you name a card, it’s too late for the targeted opponent to respond.
10/1/2009 You may activate the ability only during your turn, but you may do so any time you have priority. (In other words, it’s not restricted to only the times you could cast a sorcery.)