Rumors were created some day around january 2011, when lolo500, the creator of the map decided that they would help you to find quests , just like in Oblivion.
They are all over the city, the 80% of the populated structures at Imperial Lands have a rumor, and there are more than 200 rumors at this point. (v0.3.1)
Example of a rumor:
This one is located at Birch City:
"Kelgan the noble: I've heard about a big Oblivion Gate attacking Botternil ! Please help them, my family is there, people around this district talk about an Imperial Legion soldier named Mariah, she is looking for some help to close the gate."
As you see, Mariah is the quest giver and it is located at Botternil , rumors are 100% of time true, so be sure you will find adventures reading them.
This article is related with the quests article, if you haven't done it yet, do it.