In a brand new Developer Diary, Jessie "Vastin" King talks about the Reputation system in Lord of the Rings Online and the overall goals of the system. He also takes time to answer some burning questions on the topic, so it's definitely worth taking a look if you're a fan of building up reputation with NPC factions.
The amount of effort required to pursue reputation rewards tends to be fairly high, but we try to keep it as accessible as possible. Most of the reputations can be pursued by solo players fighting non-elite monsters on the landscape - indeed, they can even be pursued by crafters or simply by buying faction trophies from the auction house and turning them in. Call it the "slow but steady" approach to end-game rewards, if you will.
Most factions also have a way for fellowships to woo them, by fighting elite monsters in various dungeons throughout the game. This isn't meant to be any faster or slower than the solo approach, it's simply meant to allow fellowships to work together towards a goal rather than forcing them to break up and solo to do so.
The Reputation system is slated for release alongside Book 10: The City of the Kings, the next free content update for the game. If you want to read more in the diary, head over to the LOTRO Dev Corner.