Steven Feuerstein has a nice post about Oracle GUIDs. In his latest product named Qute – the Quick Unit Test Engine, Steven uses GUIDs for primary keys.
Steven wrote about how a bug in the Delphi code and the fact that Oracle SYS_GUID function was returning sequentially-incremented values, rather than pseudo-random combinations of characters (in certain circumstances) was causing an error when starting up Qute.
Steven went on to write about what a GUID is, what they are good for, how to format and use them in Oracle PL/SQL and more. Read his full post titled: Watch out for sequential Oracle GUIDs!.