And Reddit has been around for close to six years, so there's more than that celebrating an idiotic 'cakeday'. Basing my estimate off of most of the default subs having over 2 million subscribers, I'd have to guess at there being well over 3 million registered users (I've been told that the 'subscribers' only count those people who have changed their default subreddits in some way), so I'd ballpark it at a hundred thousand, give or take, with a slightly higher concentration on anniversaries of a major event such as the Obama IAMA that brought in a disproportionate number of new users.