If you asked me in 2009, a GitHub would be enough for a developer's portfolio in the context of an open-source developer. Given the mainstream status of Twitter in referencing tweets as "evidence" in online articles or participation in conferences/meetups, it may be wiser to be on Twitter to market yourself as a dev, rather than the rest of the alternatives.

Facebook, LinkedIn, Instagram and Snapchat serve no utility for a single developer but instead benefits better for an organisation.

You don't ~need~ social media, per se. I've made a decent living not relying on Twitter, Facebook, or LinkedIn. I hear about good jobs the old fashion way: Through in-person connections.

If anything, email is my social media.

I'm trying Social Detox, only trying to keep on track with HN and some Reddities.

Abandoned Facebook, LinkedIn, Tumblr, etc, too much noise.

Trying to keep Twitter, but, Twitter keep you on a social bubble, so, HN is best to capture trends.

LinkedIn is a big source of career opportunities for me, many recruiters send me messages and some had very interesting offers.

I abandoned facebook and twitter year ago. I use hn instead to kill time and watch tv series (the killing, mr robot, sillicon valley, etc)