User blog:G0LD3NF1RE/Skyrim Will Have Infinite Quests

The Radiant quest system will randomly generate new quests and tasks based on your progess in the game. Todd Howard says that you'll be able to do extra work for factions like the Thieves Guild and the Dark Brotherhood, Once you complete the scripted quest lines for each group, you can go to their respective hubs and pick up randomly generated missions.

http://www.wired.com/gamelife/2011/11/skyrim-infinite-quests/