I am getting more than a little irritated by the Hold on a perfectly reasonable questions that is marked off-topic with no explanation for how a particular rule applies.
This question does not appear to be about server, networking, or related infrastructure administration within the scope defined by the community -
I needed to figure out who the big registrars are and one way is to take a look at their client list. Also a good way to filter out the nasty creeps. Yet this question was put on hold in what appears to be a very arbitrary fashion.