I'd love to see actual data on this but I doubt that a lot of people get hired because of their online reputation. And by "hired" I mean it directly lead to a job offer instead of just getting your profile noticed and getting you started through the recruitment funnel. And of those that had an offer, how many actually took it?

Being top 1% contributor in Go would tell a recruiter you know Go but the job probably involves other technologies you need to prove yourself in. Even in the rare case that you are top contributor in every technology on their checklist, the job might still involve domain knowledge that isn't purely tech. Or they'd want to evaluate your personality.

Anecdote: not to brag given my skepticism above but so far the only online activity of mine that lead to a job offer was a Ruby Github repo on traditional AI. The catch: I am not a Rubyist and that repo was nothing more than a fork I'm studying. Long story short, I was looking for a job then, this consulting firm saw my Github profile so I got an interview. Onsite, the TL looked at my resume, visited my profile, saw the Ruby project, asked a few questions about it, and then recommended me for an offer with the hiring manager.

I did not take the job because (a) they looked desperate for anyone in the process and (b) I would've bailed anyway because I already found a company I'm set on joining. Nothing more came of it other than this HN comment.