Of course it is not :-)
But when we started talking about DBAs concerns then every byte matter.
In my work int fields are just what I need to have IDENTITY, not bigint, that is why I focus on integer type.

>The GUID is stored as 16 byte binary data. The charcter represantation of it you're alluding to, is different story. The hexadecimal representation of such value would be 32 bytes. Add four dashes and you get your 36 characters. It'll be 38 charcters if you add curly brackets.
>I'm not sure why you belive that IDENTITY is 4 bytes. It'll be 4 bytes if column type is int, 8 bytes if column type is bigint and up to 17 bytes for numeric.
>Anyway, I do not think that extra 8 or 12 byte make big difference in traffic between applicaion and SQL Server and should be major factor in decision which PK type to use.
>