Red Herring's Ryan Olson put in some serious legwork recently to try and pin down the elusive U.S. user figs for the major MMOs and online worlds out there. His study shows some great comparisons between Nielsen-tracked stats and those done by comScore, but the big takeaway is the realization of just how fudgey the numbers out there are, depending on who you ask and what factors you measure. For example, registered users are not the same thing as active users, and Olson also scrutinized engagement level-- that is, how much time users are spending logged on, on average. As Olson says:

These numbers are all over the place and I wonder about their accuracy, especially given that Habbo (see below) says an average user spends 32 minutes on the site each time they visit. Gaia's engagement figures are even higher. So they visit once each month? Riiiight. Meanwhile, the highest-ranked offering according to comScore (Neopets) is tied for third in terms of traffic. Second Life, on the other hand, boasts stellar engagement numbers from Nielsen but ranks second to last in monthly uniques. Not overly surprising.

Know what this means? COMPANIES NEED TO BE MORE TRANSPARENT WITH THEIR DATA.

Olson's emphatic statement is supported by the fact that many online worlds don't release user numbers at all, and those who do are selective, often resulting in widely variant guesses-- as the article says, GigaOm says Club Penguin has 4 million active users, while TechCrunch puts the figure at 500,000. Olson also helps illustrate his point with a "report card" showing just what types of user data (active, registered and unique users) are released by whom. According to the table, NCSoft and Second Life are the most transparent, while Millsberry, Club Penguin and Webkinz are the least.