All this proves is that the Alexa top N isn't a good metric of determining who is or isn't a monopoly. It's completely ignoring mobile apps (so Instagram/Whatsapp don't make an appearance), and it has no visibility into revenue. Reddit's current total valuation is in the small single digit billions. It doesn't deserve consideration in a conversation about the true gorillas in the field, i.e. the ones that are worth three orders of magnitude more.