One reason I still have a WoW account is it's one of the few decent MMOGs that have no F2P players.
That being said, it is stock full of the kind of players I believe the F2P encourages anyway, so I'm not sure there's much point in supporting Blizzard to avoid it in WoW.
knightnike, the whole reason publishers are adding F2P to their subscription based games is just what you said; F2P players, on average, spend more money than subscription players. It attracts the kind of player that doesn't want to make a commitment to a game - even just for a month - and doesn't want to have to buy the game up front, but will spend more money each month because they "can but don't have to".
The MMOG model now is "release the game as subscription based, get those suckers to pay for a large chunk if not all the development costs by paying $60 cash up front, and charge them $15/mo for awhile so they don't feel too ripped off when they add F2P and everyone else gets the game subscribers spent $60 on for free.
Rake in $20 million a month for a game that costs you half a million to maintain, spend $10 million on an Xpack every other year, and make over $200 million profit. Whine and cry about how you aren't making enough money, and go F2P, adding another couple of million accounts - most of which cost almost no money because they are just accounts on the books that you get to use to brag about how successful your game is, a a half million or so are giving you money as fast as they can.