Using GUIDs in Primary Keys / Clusted Indexes

Question

I\'m fairly well versed in SQL server performace but I constanly have to argue down the idea that GUIDs should be used as the default type for Clusterd Primary Keys.

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Answer 1

Drawbacks of using GUID as primary key:

• No meaningful ordering, means indexing doesn't give performance boost as it does with an integer.
• Size of a GUID 16 bytes, versus 2, 4 or 8 bytes for an integer.
• Very difficult for humans to remember, so no good as a reference id.

Advantages:

• Allow non-guessable primary keys that can therefore be less dangerous when displayed in a web page query string or in the application.
• Useful in Databases that don't provide an auto increment or identity data type.
• Useful when you need to join data between two disparate data sources across platforms or environments.

I thought the decision as to whether to use GUIDs was pretty simple, but maybe I'm unaware of other issues.