Things are booming. Nearly US$5M exchanged in January, up from US$235k in October 2005.
With the data provided by Linden Labs linked from here:
(The comments on this post are interesting, BTW)
I plotted this:
Short version: Since October 2005, 40x more folks, each spending 1/6 the hours, but exchanging 3x more money per hour.
Postscript: of course averages lie. There are sure to be massive concentrations in spending, both in terms of who is buying (big businesses experimenting) and what is being bought (land, skins). And these concentrations could be hints of a speculative bubble that will pop at some point, just like they do in the real world. After all, what if big businesses buy islands and no one visits them? They're unlikely to invest further, at least in the short term. And what if users buy cool outfits, and still can't make friends? Maybe they cash in those Linden dollars, buy some Ben & Jerry's, and crawl back to real world Saturday nights watching Love Boat reruns. At least, until a Dale Carnegie for the 21st century emerges to help us with our virtual world social skills.
Perhaps in upcoming releases of such data, LL could include some of these "who's buying what" stats? Won't be long I'm sure until we see firms cropping up that do all sorts of analysis on the SL economy. (Related issue: if economics is "the dismal science" in the real world, is it any cooler in virtual worlds?)