Categories endpoint updated
You can only use level 3 categories when creating or updating products. By mistake we had always included the IDs for the other level categories as well. For backwards compatibility reasons we're now returning the ID for the "The Store Room" category" and will remove the ID attribute for these categories in future API versions.
See documentation for details.
UPDATE (2014-07-02): we've reversed this change as we have discovered that there are cases where this change was breaking some client applications. Please note that you can still only use level 3 category IDs when creating or updating products.