While this works for freelancers/students/startupers, it doesn't work very well for people working in bigger companies.
If your interests are related to your day job, I think it's quite risky to put your code on GitHub, even if the code is not "official". While I do have a GitHub account with some code in it, that code is not really representative.
If having a relevant GitHub account becomes a pre-requisite, you may be overlooking some good people.