You'll have to pay for new map packs with SC2. Blizzard makes a killing off of their WoW subscriptions as well. Having customers pay for services outside of the actual game is very common these days, in fact Auran is kind of behind on this concept.
This is exactly one of the points I'm trying to raise, I am willing and even in favour of paying for new content, ie. a new Map Pack, (Route, Loco or Speedtree). Question is, will they also charge a premium for actual bandwidth to download this map pack.
Is it all right if I have some of that popcorn?