Is a GUID unique 100% of the time?

Question

Is a GUID unique 100% of the time?

Will it stay unique over multiple threads?

Answer 1

The simple answer is yes.

Raymond Chen wrote a great article on GUIDs and why substrings of GUIDs are not guaranteed unique. The article goes in to some depth as to the way GUIDs are generated and the data they use to ensure uniqueness, which should go to some length in explaining why they are :-)