Is GUID of SharePoint Objects globally unique? Or is there any case where it could be duplicated?
Microsoft guarantees you uniqueness inside a SharePoint-Database, not more and not less. Even considering it is a very small possibility to have duplicates, it is possible if you have multiple databases inside the same farm.
The G in GUID stands for Globally
The U in GUID stands for Unique
The ID in GUID stands for Identifier
And yes there is a once in a 30 octillion chance it is not unique
What is an octillion ?? I don't know..
But it sounds huge, and maybe a good lock-out period (in milliseconds, we should not be too harsh) on StackOverflow for people who ask questions without searching Google first.