http://wowwiki.wikia.com/wiki/Patch_1.7.0
"Reputation gains given to a player on the Alliance, Horde, or Steamwheedle Cartel factions directly will now cascade down to member factions through the middle of the Exalted reputation level."

http://wowwiki.wikia.com/wiki/Reputation?direction=prev&oldid=329828
"What is Reputation Spillover?
This is the effect seen when a Reputation gain in one Faction of a Team will raise your Reputation in all or some of the other Factions in the Team. Blizzard calls this effect "rippling."
Not all quests give spillover, and not all quests with spillover are confined to Teams. Spillover is related entirely to the quest or mob giving the Reputation. For example, some repeatable reputation quests and Alliance and Horde starting area quests (in the level 1-10 areas) do not grant spillover.

Previously, reputation spillover could not be gained for any faction above 6000/12000 into honored. If a quest would normally give a spillover adjustment to a faction and it is above this point, no faction adjustment will be shown or given to that faction. It seems that with patch 1.10 the rule has changed. You will still get spillover when you are revered."

http://wowwiki.wikia.com/wiki/Talk:Reputation
"I just recently did a major rep grind with a level 40 Tauren Druid in order to get Exalted with Org to get a Wolf Mount. I did newbie quests in all the starting areas. All quests with a quest level of 4 or less gave only their main faction's rep with no spillover, but gave full faction reward (One exception, Valley of Trials quests give both Darkspear and Org rep and I'd assume the same for dwarf/gnome newbie quests). The exception being Silvermoon for whom I could not obtain or complete any of the level 4 or under quests. For level 5 and beyond quests I received the full main faction and spillover reputation reward on all quests with no level penalty with Silvermoon quests again being the exception which gave both Silvermoon and spillover rep in accordance with the level scaled system currently detailed on the Article page. This also persists beyond the newbie areas as the BE in Stonetalon gave very little rep when doing her quests at 40 compared to the other quest givers in the area giving full rep rewards. --Roach 02:08, 30 June 2007 (UTC)
In short, it appears that under the current system, the Article is accurate in describing how Blood Elf and (presumably) Dranaei factioned quests reward rep but that Pre-TBC main factions give full rep for all their quests without regard to level. --Roach 02:08, 30 June 2007 (UTC)"

http://www.ownedcore.com/forums/world-of-warcraft/world-of-warcraft-guides/144881-reputation-guide.html
"What is Reputation Spillover?
This is the term given to the effect seen when a Reputation gain in one of the Teams will raise your Reputation in all or some of the other Factions in the Team. Not all quests have give Spillover, and not all quests with Spillover are confined to Teams. Spillover is related entirely to the quest or mob giving the Reputation. Blizzard calls this effect "rippling"."



http://wow.allakhazam.com/forum.html?forum=21&mid=129476911811788924#6
"Prior to 4.0, all reputation gains in Azeroth (as well as a few in Outland, like Telredar or Falcon Watch, and the Argent Tournament Valiants' dailies for the 5 cities) would apply 25% of that reputation to the other cities in your faction.

For example, if you completed a quest that gave Stormwind reputation and you gained 250 rep, you'd also get 62.5 reputation applied to Ironforge, Gnomeregan, and Exodar. This was not stated in the chatlog, but it worked invisibly until Patch 4.0.

This was only for quests rewarding Stormwind, Ironforge, Gnomeregan, and Exodar (or their Horde equivalents), and only quests past the first starter areas (Durotar/Elwynn Forest for example, didn't 'bleed' like this). "