I don't know that I've observed people using the terms interchangeably, and the distinction between geeks and nerds is pretty constant - what does seem to happe

I don't know that I've observed people using the terms interchangeably, and the distinction between geeks and nerds is pretty constant - what does seem to happen is that people disagree about which label ("geek" or "nerd") goes with which category. So, yeah, we probably should jettison both words.