Oh, it does! It just also means it makes it easier to find her amongst others. Imagine a toxic gas, a chemical weapon, useless against anybody else but one person. As a weapon, it's pathetic, can't even kill anyone you come across unless you use it to beat someone to death. But against that one person you need it on? That's all you need. Being unique isn't always a good thing, but that's why you need friends. That's why you would need Dark Matter.