As a hiring person I've interviewed great engineers with cool side projects who just weren't a good fit for the particular role I was hiring for. But also famously "I created homebrew" didn't get him a job at google. I've never had to use binary trees at work. :)
https://twitter.com/mxcl/status/608682016205344768?lang=en
https://www.quora.com/Whats-the-logic-behind-Google-rejectin...