I thought the theory was that they had to be unique
They're "generated" unique. That is, if you generate a Guid it's unique
across all space/time (well, ok, until about 3400AD) but that doesn't
mean you can't store duplicate values. Assume you use a Guid for an item
number, your order detail line would store duplicate guids since you
have multiple orders for an item.
-Walden
