Okay, so I do have some statistics on the number of users. This was gathered using the awards page in conjunction with my other answer here. Pay attention to the fact that this includes all users, even if they have gone inactive since attaining these awards. Rather, I feel that the growth is more important.
Jelly-Helper (wrote first answer)
2012: 25302 users
2014: 30397 users (+5095 or 20.1%)
Deckhand (reached 100 lurve)
2012: 3684 users
2014: 4026 users (+342 or 9.3%)
Sailor (reached 250 lurve)
2012: 2440 users
2014: 2667 users (+227 or 9.3%)
First-mate (reached 500 lurve)
2012: 1720 users
2014: 1884 users (+164 or 9.5%)
Mariner (reached 5000 lurve)
2012: 433 users
2014: 481 users (+48 or 11.1%)
In summary, we haven’t grown much in two years. Although we have over 30k “users,” only 4k users have reached 100 lurve. Furthermore, the small rates of growth indicate that very few users are active on this site.
In terms of mainstream users (5k+), there have been only 48 additional users in two years. This really shows that our current userbase is stagnant. Almost every user on this page is over 10k, and there have only been 263 users who have ever reached that rank.
To put an upper bound on the number of active users, we can assume that any reasonably active user has crossed either 500 or 5k lurve milestone sometime in these past 2 years, or has already reached 10k. This gives an upper bound of 164+48+263=475 active users over two years. Of course, chances are that not nearly all of those users are currently active.
So, in terms of active users, I think that “a couple hundred” is a reasonable estimate.