But critics argue that the eye-popping, seven-figure total is, at best, misleading. As a result, Second Life publisher Linden Lab is coming under increasing fire from bloggers and gamers who say the virtual world's creators aren't giving their customers the full story.
Not surprisingly, this scrutiny comes as an increasing number of real-world companies, to tech giantsand , set up virtual offices inside Second Life, and mainstream media outlets like and The New York Times devote an increasing amount of coverage to the 3-year-old creation.
"We're being asked to believe that this is the future of the Internet," said Clay Shirky, a writer and professor at New York University's graduate Interactive Telecommunications Program, referring to the grandiose hype surrounding Second Life and its cultural significance.
"If you're being told that something is the future of the Internet and the arguments are based on the incredible popularity, the first thing you want to understand is how popular it is," Shirky added.
As of Wednesday, Linden Lab reported that there were 2,325,015 "residents" of Second Life. The company defines each of those as representing "a uniquely named avatar with the right to log in to Second Life, trade currency and visit the community pages."
Here's the problem: that total does not equate to what is commonly considered by most Web or online businesses as "active users," in large part because many people who sign up for Second Life try it once and never come back, and because individuals can have as many as five different avatars, each of which would count as a "resident."
The real number of active, individual users who log in on a recurring basis (users who sign up and return on an ongoing basis, though Linden Lab doesn't specify how often that is), is more likely in the 200,000 to 230,000 range, according to internal metrics used by Linden Lab, as well as calculations by others in the industry.
, for the uninitiated, is a virtual world that allows anyone to join and participate for free and create and own any kind of clothing, vehicle, building or other object. Linden Lab makes most of its money by charging players use fees for virtual land they buy and build on. There are also 42,400 "premium" accounts now in use. These are required for users who want to own land, and which cost a minimum of $9.95 a month.
Some may wonder why the exact number of residents constituting the Second Life population really matters. To investors and advertisers, it matters a lot.
In November, Linden Lab CEO Philip Rosedale that "although Second Life is still challenging to get used to, about 10 percent of newly created residents are still logging (in) weekly, three months later....That percentage hasn't changed much with the much higher rate of new users."
In an interview with CNET News.com Tuesday, Linden Lab CTO Cory Ondrejka reiterated the 10 percent conversion rate, although he also said that for technical reasons, the company does not have a true number of active users.
When asked if the rate meant that there were currently about 230,000 active Second Life users, Ondrejka said, "That's a good number for conversion... That math is right."
That number is also supported by calculations done by a longtime insider of the online games industry.
Doing the math
First, the insider said that one common industry metric for arriving at a number for active users is to multiply the number of peak concurrent users by 10. Since Second Life has had peak "online" numbers in excess of 20,000 recently, that would extrapolate to more than 200,000 active users.
The industry insider pointed to another measurement, which is to look at the monetization ratio--the percentage of users who produce revenue for the publisher--of about 10 percent for digitally-downloaded online games. That, the insider said, jibes with Linden Lab's 10 percent conversion ratio and again points to the 230,000 active user range.
The question of how many people actually use Second Life has always been hotly debated, in particular because it is free for anyone to join.
While 42,400 people pay for premium Second Life accounts, that number pales in comparison to the more than 7.5 million people who pay for subscriptions to Blizzard Entertainment's World of Warcraft. Blizzard charges $15 a month to play WoW, though the company said that about 3 million of those subscribers are in China, where the monthly fee is much lower. Still, WoW brings in tens of millions of dollars a month in revenue.
For its part, Linden Lab has said that Second Life is nearly profitable, largely on the strength of revenues from land use fees.
So why the controversy? Critics contend that journalists don't understand the difference between "registered accounts" and "active users," and that execs at Linden Lab haven't exactly gone out of their way to clear up the confusion. Because Linden Lab prominently reports more than 2 million residents, many articles have said that Second Life has more than 2 million users.
Ondrejka argues that this is still accurate.
"The total residents, which we have always talked about, is the right number to represent users," Ondrejka said. He pointed out that Linden Lab also prominently reports the "trailing" number of residents who logged in within the last 60 days, which as of Wednesday was 844,310.
That means, of course, that at best, fully 63 percent of registered accounts have not logged in within 60 days.
There's another issue with that figure: the game industry typically reports users logged in within the last 30 days, not 60. The 30-day number, as of Wednesday, was 534,738 for Second Life. That means 77 percent did not log in within 30 days.
Ondrejka said that Second Life is different from traditional online games. He pointed to a recent study Linden Lab conducted over six months in which the company examined member usage.
He said that 30 percent of users had gaps of one or two months between log-ins. And that's why the company prefers to put the 60-day trailing number on the SecondLife.com front page.
Ondrejka said it is nearly impossible to arrive at a true number of active users because of the vagaries of the credit card numbers and IP addresses employed by users, and the fact that users can have multiple accounts.
"I'm open to any Internet service that has a solution to the Internet identity problem," said Ondrejka. "We don't know who's at the other end of the keyboard."
Still, because Second Life users frequently return after long times away, he said Linden Lab sticks to its "resident" definition.
Other virtual-world and online-game veterans acknowledge that it's very hard to figure out how many real users there are.
"With the rise of non-subscription services, the industry is having to adapt to different metrics altogether," Raph Koster, a designer of Ultima Online and former chief creative officer of EverQuest and Star Wars Galaxies publisher Sony Online Entertainment, wrote on his blog. "The original metric people used, of course, was subscriptions. This is a great metric for assessing how much revenue a game is getting, but it does have a few oddities in terms of determining the popularity of a game."
Koster wrote that his favorite measurement is "average weekly unique" users.
"Basically, counting how many people are online at any one time, or counting how many are paying, doesn't tell you how many are actually playing," wrote Koster. "But counting how many people logged in each given day, and then averaging that out across the week to smooth out the daily fluctuations will give you a very good sense of how many people are actually playing."
In truth, there may not be one easy answer to the virtual census problem.
"The real metrics that matter are 'number of daily unique logins' and 'average length of sessions,'" said Michael Steele, a vice president for the online game middleware software developer Emergent Game Technologies. "No one cares about raw registrations anymore."