So now you could scrape the name of every GitHub user and their email if it is public.
https://api.github.com/users?since=0
And iterate on. They even give you a HTTP header for the next URI:
Link: <https://api.github.com/users?since=135>; rel="next"
There is a rate limit of 60 (per hour), but if you use oauth then it's 5000. See http://developer.github.com/v3/#rate-limiting
5663608 / 5000 = just under 48 days worth of non stop API harrasment... maybe that explains why github keeps going down, someone is already trying this out :P