According to Broken Toys (aka Scott Jennings/Lum the Mad), it looks like Blizzard is introducing a keychain security dongle called the Blizzard Authenticator.
It looks like an interesting option for anyone really worried about the security of the account, as it enables proper two-factor authentication. You will be able to purchase it from the Blizzard store for $6.50, which is a pretty reasonable price, in my opinion.
The only issue is that this is optional, and some of the people who would get the most use out of this will not hear about it or pick it up.
It will be interesting to see the effect of this Blizzard Authenticator on the game. For example, account sharing is rampant among the high end. But the people at the high end also have the most to lose to a hacked account, and are the mostly likely to purchase and use the Authenticator. And that may cut down on tactics like getting someone else to play your character in Arenas.
It might also have an effect on guilds. A lot of guilds are very concerned about security for the Guild Bank. I can see a guild requiring that all its members, or at least all the officers, purchase and use the Authenticator.
It's good to see that Blizzard has been taking security more seriously lately. They took my advice on disabling hyperlinks on the official forums, and are now introducing a good two-factor authentication system. However, I still think that the default game experience needs to be a little more secure.