Well at lest Blizzard, hopes that it will become safer with the introduction of there new "Blizzard® Authenticator". What is it? Well, its a key fob device (that can be purchased for $6.50 from Blizzard's Online store), that randomly generates a six-digit number when a button on the device is pressed. This number is then used in conjunction with your log In ID and password when logging into World of Warcraft. Without this number you will not be able to log into your account. (I'm assuming if you bought one of these devices, as Blizzard calls it an "optional security measure"). The number that is generated is only useful once and is only valid for a short period of time.
So in other words, its similar to the "Paypal Security Key". As for if it is as secure, as Paypal's "Security Key", only time will tell. What I do know is that is will, help people who had there account hacked or knows someone that had their account hacked to, feel more secure every time they log in to their account.