Ever asked yourself that? In a genealogical sense it scares me to hear that.
Sourcing my materials is not my favorite part of genealogy. Truth be told I'd much rather be out chasing new stuff, chasing stuff that I haven't worked on, but sometimes you have to do the homework before you can play.
In the world we live in where "click & claim" is the name of the game for so many "name collectors" - sourcing is something often ignored. What I do not understand is if you dont' know where you got it from how can you judge how valid your information is?
Sourcing is not rocket science, and to be really honest, you don't have to source it to make your English teacher happy. Okay, so you don't plan on publishing - you still need to state where you got the information - FOR YOU!
You should put enough information in your source that should the need arise for you to check out that source for other information you can look at your source and go right to it. Including the who, what, when, where items really does help.
I see alot of people, especially on one of the more popular genealogy websites that do not share ANY of their sources for the material. One of my favorites is "so & so's gedcom". Now how does that help you? Twenty years from now is "so & so" going to be around for you to ask about the information they gave you?
Trust me, sourcing for yourself is the way to go. Your peace of mind, knowing that you have the source documentation to back up your dates & information is one of the greatest feelings you can have. Take a few minutes and document your work! You'll be glad you did.
Remember, Genealogy without documentation is mythology!
If you are a librarian or program chair for a library or society I have a talk by this same name. Email me if you are interested.