I posted this to support but I'm going to post it here as well.

I have an environment with three areas.
Development
Staging
Production

Generally, objects are created in Development and documents are created in Staging. However, we build the intial site tree in Dev and we often create "dummy" content in Dev to test our objects.

The problem that we are having is that Identify-generated fields are being stored as foreign key values in CMS_Document.DocumentForeignKeyValue and CMS_Tree.NodeClassID.

What this means is that if a developer creates a test instance of DocType of XYZ on Development at the same time that a content editor creates a real instance of XYZ on Staging they can both have the same Primary Key field in the DocType table which means they have the same DocumentForeignKeyValue value in CMS_Document. Now when I sync these two documents (one from Dev -> Staging and one from Staging -> Dev) they will get new Primary Key values but the foreign key value in DocumentForeignKeyValue will no longer match. This is a problem.

As I look at CMS_Tree and CMS_Document I see many fields that hold foreign key values that are associated with Identity columns. CMS_Document has multiple user fields, DocumentNodeID, PageTemplateID, etc. CMS_Tree has NodeClassID, NodeParentID, NodeOwner. Why? It's almost guaranteed to fail in a multiple server environment. I know that GUID don't query as well as integer but this is a significant problems that needs to be fixed.