A friend sent me this link - Apples and Oranges - to an article on Second Life metrics - it's the best one I've read, so far.  Read a bit of the post but need to go back again when I'm less tired and have more time to spend.

Also briefly looked at Top 25 Brands Measured By Traffic? which I also need to read much more closely; I'll write in depth about both articles, perhaps later next week.

Much thanks to http://www.ugotrade.com/ (Tish Shute) for bringing both articles to my attention today.