White says the memory and history are not the same thing, that memory often leaves the lies, cruelty and other things that most people want to forget.
Oral history can be important because it gives the historian a more personal look at the history that is being told. If there is an oral history of a fighter pilot in WWII, a historian could find out the feelings the pilot had, what he smelled, and what were his fears while flying. It seems like there aren't many sources that a historian can access that can give those sorts of details.
However, oral history is based on memory, and as White said, memory leaves out many details. An event can happen and everyone that viewed it could say something different about it. An historian can use an oral history but I would say that they should have other sources to back it up as well. If you have other evidence that is similar to the oral history, I would say that it would be a good source to use. If all you have is an oral history though, I think it might be fairly weak evidence for an historian.
