Unique Users

In this thread, Vasudha said "Also, in case you are wondering how many accounts logged in: about 60,000 accounts logged in Mar-06. (approx. 47,000-Basic & 13,000-Premium) Hope this answers all your qusetions."

There are a number of people interpreting this stat to mean that there are at least 60,000 unique users of Second Life.

How many of those 60,000 accounts belong to unique users. At least, how many of them are tied to unique credit cards?

*edit Here's a spinoff thread that developed after this posting and might help clarify our wonder.