This question and its answer explain how bulk inserts will render FK as untrusted, as bulk inserts are not completely checked (only PK and UNIQUEs) . I also know that temporarily disable of a FK may lead to untrusted status.
My current project uses a rather small database (< 3GB) and typical table count is less than 200K rows. However, integrity is very important, so I rely heavily on FK constraints (integrity is much more important than speed).
Question: is there any other mechanism (besides disable and BULK INSERT) that can produce untrusted foreign keys?