I like to use the things I geek out over in my career, which is somewhat obvious by the fact I help run a blog about the very subject. I'm a big advocate that hobbies, jobs, and interests really should be mostly the same thing.
However, it's too easy to get caught up in our own obsessions, our own geeky, our own fanning. Sure we can learn a lot from our obsession with video games, our passion for digital art, and our interest in writing.
However if you really want to be a passionate fan-to-pro type you need to study the geekery of others.