Isn't your Hackernews account a "Social Media" account? Maybe it is, maybe it's not. We have no idea what the Governments definition of a Social Media Account is.
Interesting point, they'd have to either give a strict definition or a list otherwise I actually have no idea what to put. What about my ancient XDA Developers account that I don't even remember the username of? Would anyone with a Google account need to give that as YouTube exists?