GUIDs also add a level of security, as was noted in the article, which is especially important in government and military developed applications. I develop a number of security-related and classified web and client/server applications, and using a GUID as the primary key helps prevent users from seeing records that are not theirs. If we exposed an Identity PK that had values 1 and 4 for a specific user, it doesn't take a rocket scientist to figure out that there are probably records with IDs of 2 and 3 too. Depending on how securely written the app is, it may or may not be easy to get at those records. Very difficult to "guess" like this when using GUIDs. Despite the performance hits a GUID may come with, we find that the benefits of GUIDs from a security point are worth it. This logic probably has merits in other arenas too, especially e-commerce and financial-related systems. My 2 cents... Steve