Given Second Life's peak concurrency growth rates over the last few months (it was 74K on November 3rd) the world was due to hit 75,000 today, but instead, kept right on growing, and only began receding after hitting around 76,000. Late last week there was a round of salacious (if not very original) international news articles about virtual-to-RL adultery in Second Life.
(Mitch Wagner of Info Week has a smart round-up here.) This likely contributed to the extra spurt of activity, so to speak. Which is a mystery of several layers:
How many of these new users are interested in committing virtual adultery... and how many of them are real life partners of now-suspicious SL users, looking to catch them in the act?