New Prince of Persia to have Live Component
IGN is running a story regarding the upcoming Prince of Persia: Warrior Within. The Xbox version of the game will have downloadable content and leader boards thanks to Xbox Live. The leader boards will cover two self-contained competetive types of play: Timed Missions and an Arena. Info also available on the official site.
Sometimes yes, sometimes no. It depends on the game. Ghost Recon: Island Thunder, for example, had more content download (for free) than shipped with the actual game, pretty much. I guarentee that we'll be seeing many downloadable maps for Halo 2 as well. As for Prince of Persia, I'd guess there may be just a handful of these maps, not unlike Splinter Cell: Pandora Tomorrow, which just had two.