@everyone who thinks the statement is about characters not accounts
Why on earth would Blizzard care or care to reveal the number of characters that don't reach level 10? This is clearly about accounts because Blizzard would not be talking about it otherwise. (honestly, I don't know how you can read "70% of World of Warcraft players" and think that this is about anything but accounts)
I know it can be hard for someone who is so commited to the game and knows so many others who are committed to the game to accept that you are the exeption and not the rule. But the point is really that you never see these other people. They join, play for a few hours, find it boring and never return. And you (and the rest of the regular player base) are oblivious to their presence.
If you want to put a positive spin on this, there are likely 15 million plus players who have exceeded level 10 over the years, meaning that WoW has had 50 million plus people try it. That's pretty impressive.
(btw, I had never tried WoW because I got bored with several other mmorpgs before getting more than a couple of levels in and while Blizzard did much to fix the problems other people had with mmorpgs, WoW includes everything I disliked about the mmorpgs I have tried)