Blizzard can make authenticators a mandatory feature on all Battle.net accounts.
There are many pros and cons such a move would bring about. Let's examine the cons first since everyone likes to complain about stuff. The largest con would be that people would be required to have a physical piece of equipment specific to WoW and other Blizzard games. Some people would obviously not be okay with this and cancel their subscription, and others would not understand how to push a button and punch in numbers (I'm not kidding). There would be a large cry from people around the net, particularly people who enjoy scamming others out of gold and their accounts, but those are easily enough ignored.
Blizzard could get around these negatives by simply giving away authenticators to everyone who doesn't have one -- make it part of the $15/month subscription. You have a subscription, you get an authenticator to keep no matter how long or short your subscription lasts. For those that don't have a subscription of some sorts or are playing on a trial account – you play on a separate server that is jailed from the rest of the servers. It would be a large one time buy on the part of Blizzard for all its customers, but it would be worth it in the returns of lessened customer service (all those GMs don't have to deal with "OMG my accounts been haxors!" emails).
And really, seeing a little authenticator in every WoW box on store shelves would send a clear and unmistakably loud signal to the rest of the gaming industry -- your products need to be secure. You need to keep your customer's accounts safe, and this needs to be a top priority.
Some might say that another con is the hardware and software required to service millions upon millions of players -- however such hardware is already in place in banks and government agencies. Your authenticator is little different than what they use, and the backend serves are even similar.
Now for the pros -- we've already outlined two major ones; leading the gaming industry and decreasing GM work load. In particular these days the amount of work GMs are doing has clearly become more than Blizzard can currently handle. Tickets are in queues for days right now, and you're one in a million if you actually get to talk to a GM in any reasonable amount of time.
Another added pro to this idea is that the amount of gold selling and account selling would drop dramatically. I don't have much fear of giving virtual items away when it comes down to it, even my whole account if I were so inclined (note: read carefully, I am in no way supporting account selling). But I do have a big problem with sending someone an authenticator I don't know -- and I sure as hell would never give my address to some random guy that owns a WoW account I want to buy.
Creepy guy living in his mom's basement can give me all the gold and accounts he wants. But touch something he's touched? Yuck, no thanks.
Of course this is only a 50,000 ft. overview of the situation, and there are a lot of details that would have to be worked out. But it's something that I hope Blizzard seriously considers. Use this opportunity to make WoW and all the Blizzard properties the safest and most secure form of virtual interactive entertainment out there.
What do you think? Would you be okay with Blizzard making authenticators mandatory?