Thing is that they believe they can make more dollars than they do with the current model. Which is roughly 10m players * 20$ * 12 months. They need to get that from somewhere in the end. And I doubt they can trick more players into the game because it's ftp (and who are actually gonna spend a lot of $) to make up for that.

I have a competitive nature and it means that I want to have the same features at my disposal as any other players. Making those 'paid' upgrades is not something I fancy. Because that can be something endless. They basically can add unlimited new features. I've had a really bad experience with the game I've previously played, and the wow concept where I knew what I was going to spend seems like the best way to me.

There is another FTP model however where player A buys a certain currency with real life money, and that currency is trade-able in the game for gold. With that currency player B can get the 'paid upgrades'. So basically the very casual player who just spends way too much money pays for the upgrades of an addicted players. Both sides are happy. The only downside to this model is the inflation on the currency/gold rate, whenever you take a break.

But then again, Blizzard has created a top game, and their decisions usually make sense one way or another, nor are they too proud to admit mistakes (remember realid / forum). So who knows, they 'll come up with a new innovative ftp model that will satisfy every kind of player.