A few days ago I was reading another blogger's post about source's and citations and how that validates a tree. Unless there is valid facts to back up the information that can you trust it.  If I am doing research on names, or people, I always will verify that it came from a valid source, but after taking a look at my 915 names in my family tree, I started to notice something.
While I expect to have a source/citation for the info, for the most part it never made it into my family tree, which now has me backtracking and creating citation information, and placing info in as best as possible.  With the hopes that with futre information I add a citation, and no put it in by blind faith. 
I too wonder how many tree's started without citations, and what made the user finally decide that it would be in the best interest to put citations of were they recieved the information.