Skepticism about the number of users within SL...

http://many.corante.com/archives/2006/12/12/second_life_what_are_the_real_numbers.php
Second Life may be wrought by its more active users into something good, but right now the deck is stacked against it, because the perceptions of great user growth and great value from scarcity are mutually reinforcing but built on sand. Were the press to shift to reporting Recently Logged In as their best approximation of the population, the number of reported users would shrink by an order of magnitude; were they to adopt industry-standard unique users reporting (assuming they could get those numbers), the reported population would probably drop by two orders. If the growth isn’t as currently advertised (and it isn’t), then the value from scarcity is overstated, and if the value of scarcity is overstated, at least one of the engines of growth will cool down.
There’s nothing wrong with a service that appeals to tens of thousands of people, but in a billion-person internet, that population is also a rounding error. If most of the people who try Second Life bail (and they do), we should adopt a considerably more skeptical attitude about proclamations that the oft-delayed Virtual Worlds revolution has now arrived.