My understand...

INS had clearly noticed that notarized copy = original, so for the important document, never give up it, you should always keep the original one. Whereever reqire original document, just make a copy and notarize it. Because the US government related offices never return any documents you submitted to them, even if it is important to you.
For example, see instruction of I-140, INS had declared that they never return any document, even if they are important for applicant. They had suggested that for important document, just submit notarized copy.