From the rules errata:
To stake an opponent, an attacker must target the heart. Wielded in hand, a stake calls for a Strength + Weaponry roll. Fired from some kind of projection device or thrown, a stake demands a Dexterity + Firearms or Athletics roll. The damage your character inflicts is lethal but must also be sufficiently high to pierce muscle, bone and organ. All totaled, efforts to stake a resisting target are at a –3 dice penalty; an exceptional success must be scored to strike all the way to the heart. If an ordinary success is achieved, damage is done, but not enough in the proper spot to have any special effect on a monstrous target.
This seems like a herculean task for most characters within World of Darkness. So much so that I have never heard of a player seriously choosing this as a valid strategy. Between the -3 penalty and a requirement for exceptional success it seems to fly in the face of the inherent vulnerability of vampires to this attack. Is the message White Wolf is conveying is that this is a largely useless technique, or could other rules influence the circumstance (a held down or sleeping vampire looses its -3 bonus for example).