SL Social Network: Less Than 100K Users, Says Google
So I wondered last week how many people are actually using my.secondlife.com, the internal SL social network, on a regular basis, and here's a pretty good estimate: According to Google Ad Planner, the site gets about 84K monthly visitors, with 32K of those from the US. Yes yes, a site user is not the same as a registered user with their own profile and such, and so the number of people actually using the social network to post updates and such is likely less than 84K. (Significantly less, I'd wager.) That said, traffic approaching 100K is pretty good, especially if you assume the active, meaningful Second Life userbase is probably 400K monthly uniques. So overall, it's not a bad idea to create a my.secondlife.com profile of your own, especially if you're an SL content creator. In which case, follow Cajsa's advice.
Then again, if you take Google's numbers to be reliable, you probably don't want to spend too much time doing so: