I'm not sure, but this check might prevent non-global teams from being saved if a global team with the same name exists. You might need to do something like this: http://stackoverflow.com/a/18103038/54696
Add tests for the following:
- a user-owned team named "foo" is considered valid, even if a persisted global team named "foo" exists
- a persisted global team named "foo" is considered valid (doesn't see itself as a conflict when validating uniqueness)