[kitcar]

Depends on where you want to work / what you want to do - If you are a software engineer, a strong Github/Stackoverflow presence which demonstrates your technical competency (and that you can draw attention to early in a cover letter) would likely help you stand out more than a standard linkedin profile IMHO.

[dragontamer]

Or not. My current job has nothing to do with Github / Stackoverflow presence.

I do know people who have made connections through Github / LinkedIn / StackOverflow. But I personally don't have an active account on any of those three.