Terra Nova's Mike Sellers has put up an excellent post trying to decipher what 'user numbers' really mean in online gaming, contrasting the often massive 'registered user' numbers cited by free virtual worlds with the more locked-down active and paying subscribers in MMOs.

Citing Habbo Hotel's '40 million subscribers' as a good random figure to attack, he points out: "How many of HH’s 40M members are old defunct accounts (I know at least a few are old ones of mine)? Similarly I doubt that CokeStudios really has 4M active users – they say those are “registered users” and that’s a very different thing. As Daniel James said recently here on TN, 'Puzzle Pirates has had over 1.3M 'users' if you count registered accounts' but actually has 'substantially less than that, however, at ~23k subscribers/equivalents.'"

Whatever the case, Sellers points out in his conclusion: "How can we accurately assess a world’s population size? This is important for both reasons of social research and commercial viability. It is important that as MMOs continue to grow as a cultural phenomenon that we neither downplay their impact nor over-inflate their growth." So... how long is that piece of string?