It depends what your goal is. If you're trying to get a specific person to say a certain thing, then it works well. If I wanted you to confess to a conspiracy with my political enemies so I could execute them, the fingernail removal strategy works fine.
If you're trying to figure out the truth in a fluid and confusing environment, then it doesn't work well because it motivates the victim to do whatever they can do to end the conversation as quickly as possible.
If you're trying to figure out the truth in a fluid and confusing environment, then it doesn't work well because it motivates the victim to do whatever they can do to end the conversation as quickly as possible.