Indeed. When I'm doing a technical interview, and I ask a question, I want the person I'm asking to tell me if they don't know the answer. If they tell me that they don't know the answer, I'm more confident that when they are stuck on a problem in the real world, they will come and ask someone, or look it up, rather than just trying to bullshit their way through. In the real world, guessing can be considerably more dangerous than admitting that you don't know something and thus taking the effort to actually find it out.
