Out of curiosity, number of sources?

Question:

Out of curiosity, number of sources?

I was wondering, of those of you who are actually doing genealogy, how many sources do you want before you take the information as fact?
For example, you find a possible ancestor listed in the 1880 census only, and no where else. Do you add that person to your tree, or do you wait until you've found at least one more source for them?
I usually want 3 sources, but will settle for 2 if they are good ones, like BDM records. However, I have run into a lot of brick walls where I can only find one source for that person. I'm not sure whether to go ahead with the line, or wait. So I was just curious as to what others do in similar situations.

Best Answer - Chosen by Asker: The general rule is 3 sources. If I have less than that, then I "pencil" them in. If I cannot find more sources, then they sort of become permanent. I have settled for 2 sources also. I don't like it, but I except it until another source comes along years later.