They didn't give them those powers. The company just sort of tagged them in order to keep track of them. I'm pretty sure Matt had displayed his powers before getting caught by the company the first time. Clare was never caught by the company, and so doesn't have the "teeth marks" and I guess we don't really know about West (Is that his name, or is it ike Wes or something? I don't know, for some reason that name pops into my head. Clare's boyfriend.) but he didn't say that he got the powers after being taken by the company. The way I though he made it sound was that he thought they tagged him because of his powers, implying he had them before.